JP2602802Y2 - Current switch circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current switch circuit for driving a load such as a light source such as a light emitting diode (hereinafter, referred to as an LED) or a laser diode (hereinafter, referred to as an LD) in an optical communication transmitter. .

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
For example, there is one described in the following literature. Reference 1: IEICE Technical Report (Technical Report of IEICE), 89
[226] (1989) Kijima et al., "Broadband LSDN Optical Transceiver for Subscriber System (OCS89-34)", p. As described in Documents 1 and 2 described above, for example, an LED or LD is generally used as a light source in optical communication, and an emitter-coupled device is used for driving the light source. A logic (hereinafter, referred to as ECL) type current switch circuit is often used. 2 and 3 show examples of the configuration.

FIGS. 2 and 3 are circuit diagrams showing a configuration example of a conventional current switch circuit. The current switch circuit of FIG. 2 is an unbalanced input type circuit for driving a light source D composed of an LED or an LD, and is an NPN transistor (hereinafter referred to as Tr) constituting an ECL type current switch.
1, 2 and 3, an external emitter resistor 4 of the Tr 3 for sink current of the ECL, and a DC bias current source Ib of the light source D are provided. In FIG. 2, Ccb is the collector-base capacitance of the ECL sink current Tr3, and Cs is the Tr3
Vp is a base bias power supply of Tr3. DC bias current source I of light source D
b is generally unnecessary when the light source D is an LED (Ib =
0).

Since this current switch circuit is of an unbalanced input type, a transmission pulse signal source S having an ECL logic level is applied to the base of Tr1, and a reference power supply Vr for providing a threshold level of ECL is applied to the base of Tr2. I do. The switching current Ip flowing through Tr1 and Tr2 is controlled by the base bias power supply Vp and the emitter resistor 4. When the potential of the signal source S is higher than the potential of the reference power supply Vr (logic “H”), the light source D is turned on, and when it is lower (logic “L”), it is turned off. The current switch circuit shown in FIG. 3 is a circuit of a balanced input system, and has a configuration in which an inverted-phase signal source r of the transmission pulse signal source S is applied to the base of Tr2 instead of the reference power supply Vr. In this current switch circuit, the light source D is turned on when the potential of the signal source S is higher than the potential of the reverse-phase signal source r (logic "H"), and conversely when the potential of the signal source S is higher (logic "H"). (L)).

[0005]

However, the conventional current switch circuit has the following problems. (A) FIG. 4 is a waveform diagram of the switching current Ip in the current switch circuit of FIG. In the current switch circuit of FIG. 2, when the signal source S changes from “1” to “0”, T
The collector potential of r3 also fluctuates at the same time, and the capacitances Ccb and Cs
Charge / discharge current is generated. Considering the transient state of the light source D from the off state to the on state, as shown in FIG. 4, the switching current Ip (steady state Ip) determined by the base bias power supply Vp and the emitter resistance 4 and the charging current of the capacitors Ccb and Cs initially Since Ip1 is added, the current temporarily becomes large, and then the discharge current Ip2 for the overcharge of the capacitors Ccb and Cs is subtracted, and conversely, the current becomes small. Then, at the end of the charge / discharge, it finally reaches the steady state Ip. Therefore, the waveform of the switching current Ip is a waveform including ringing. The absolute value of the ringing current depends on the values of the capacitors Ccb and Cs and the amount of fluctuation of the collector potential of the Tr3 (approximately the magnitude of the input amplitude) regardless of the magnitude of the steady state Ip. In the light source drive of optical communication, Ip
A current range of about 5 to 100 mA is used. For example,
Ip (max) = 100mA, operation Ip = 10mA,
When the allowable current value is large (the Tr3 size is large and the capacitances Ccb and Cs are large) and the actual operating current is small, the ratio of the ringing current to the steady state Ip may exceed 200% (the ratio of the peak value).

(B) In the current switch circuit of FIG. 3, the reference power supply Vr is replaced with a signal source r having a phase opposite to that of the transmission pulse signal source S, and a balanced input method is used. for that reason,
Since the fluctuation of the collector potential of Tr3 during the transition is smaller than that of the circuit of FIG. 2, the amount of ringing is reduced.
However, since the transient response speed of ON and OFF of the ECL is generally different, the transmission pulse signal source S and the negative-phase signal source r do not become exactly in opposite phases, and a considerable amount of ringing remains. The ringing of the switching current Ip of the optical communication transmitter disturbs the transmission light waveform, causing troubles such as a malfunction of the automatic power control of the light source D and an increase in the error rate on the receiving side. Therefore, conventionally, either the signal pulse width is increased to such an extent that ringing can be ignored (constant speed operation), or the signal pulse width is used only around Ip (max) where ringing is not conspicuous (a narrow Ip range). However, this has greatly limited the speeding up and generalization (realization of a wide Ip range). Therefore, it has been difficult to provide a current switch circuit that is technically sufficiently satisfactory. An object of the present invention is to provide a current switch circuit that solves the problem of the prior art that it is difficult to reduce the ringing of the output current without lowering the response speed.

[0007]

Means for Solving the Problems] To solve the above problems
Meanwhile, the first device of the present invention is an optical communication transmitter or the like.
In the current switch circuit, the first node and the second node
The conduction state is controlled according to the potential applied to each node.
A first potential node controlled and supplied with a first potential;
Electrically connected to a second potential node to which a second potential is applied;
Electrically and in parallel with the third node
A first Tr and a second Tr connected to a column,
A first potential node between the first potential node and the third node;
Controls the amount of current flowing to a load connected in series with one Tr.
Differential switch means, and a first input terminal and
Potentials respectively applied to the
3 according to the current flowing through the third node.
The node responds to the magnitude of the current flowing through the third node.
Means for applying a potential having a potential difference of the same magnitude
I have.

In the second invention, the current switch of the first invention is used.
In the switch circuit, the magnitude of the current flowing through the third node
Means for giving a potential having a potential difference of a magnitude corresponding to the magnitude
Is proportional to the magnitude of the current flowing through the third node.
Means for providing a first current of magnitude to a current responsive node;
The first input node electrically connected to the current response node;
Power terminal and the second input terminal, respectively.
The first node and the first node depending on the position and the first current.
The second node has a magnitude corresponding to the magnitude of the first current.
Means for applying a potential having a potential difference of
You.

[0009] In the third device, the first or second device is used.
In the current switch circuit, a first power supply of the first Tr is provided.
A pole electrically connected to the first potential node via the load
Connect and electrically connect the second electrode to the first node
And a third electrode connected to the third node via a first resistor.
And electrically connects the first electrode of the second Tr to the
The first potential node to which the first potential is applied is electrically connected to the first potential node.
And the second electrode is electrically connected to the second node.
Then, a third electrode is connected to the third node through a second resistor.
Is electrically connected to the

[0010] In the fourth device, the first or second device is used.
In the current switch circuit, the first current is equal to the current
The means for providing to the responding node is such that the first electrode is the third node.
The second electrode is electrically connected to the
Electrically connected to a first current control terminal provided;
The third Tr in which the third electrode is connected to one end of the third resistor
And a first electrode electrically connected to the current responsive node.
And a second electrode is electrically connected to the first current control terminal.
And a third electrode in which a third electrode is connected to one end of a fourth resistor.
4 Trs. Then, the third and fourth resistors are connected.
The other end of the resistor is electrically connected to the second potential node.
You.

In the fifth invention, the current switch of the second invention is used.
In the switch circuit, the magnitude corresponding to the magnitude of the first current is
The first electrode has a fifth resistance.
Electrically connected to the first potential node through
Is a first input terminal to which a signal from a signal source is provided.
And a third electrode electrically connected to the current responsive node.
Electrically connected to the fourth node electrically connected to the node
The fifth Tr and the first electrode are connected via a sixth resistor.
And electrically connected to the first potential node,
The pole is connected to a signal from a reference
And a third input terminal electrically connected to the
A sixth electrode electrically connected to the fourth node;
Tr. And the first or second input
According to the relationship between the levels of the potentials applied to the force terminals, the first
And the relationship between the levels of the potentials applied to the second node is determined.
Configuration.

In a sixth aspect , the current switch of the fifth aspect is provided.
In the switch circuit, the first electrode is connected to the first potential node.
Electrically connected, and the second electrode is connected to the fifth Tr
Between the first electrode and the fifth resistor, the fifth Tr
A third electrode electrically connected to the first electrode and the fifth resistor;
An electrode is electrically connected to the second node via a seventh resistor
And electrically connected to the second potential node
A seventh Tr and a first electrode connected to the first potential node.
And the second electrode is electrically connected to the first electrode of the sixth Tr.
Between the sixth electrode and the sixth resistor.
A third electrode electrically connected to the first electrode and the sixth resistor;
Is electrically connected to the first node via an eighth resistor.
And electrically connected to the second potential node.
And an eighth Tr connected.

In a seventh aspect , the current switch of the sixth aspect is provided.
In the switch circuit, when the first and second Trs are conducting,
The current at the time of conduction is represented by IP (on) and IP (of
f), the electron charge is q, the Boltzmann constant is k, the absolute
The temperature is T, and the third Tr is a bipolar Tr.
The emitter area of the third Tr is A3, and the fourth Tr is
Bipolar Tr, emitter area of the fourth Tr
A4, and the grounded emitter current gain of those Trs is HF.
Let E be the value of K1, K2, K3 based on the following equation:
By setting the current and temperature of the drive factor m
It controls the dependence characteristics with respect to it. n = A3 /
A4 = fourth resistance / third resistance IP (on) >> IP (off), IP = IP (on) m = Ln (IP (on) / IP (off)) (where Ln (); natural logarithm) ) Rc = the fifth resistor = resistance of the 6, Re = first resistor = first
Rb = 7th resistance = 8th resistance (Rb / n-Re-Rb / (1 + HFE)) = K1 Rc * cm * k * T / q = K2 (*, multiplication) Δ (Rc * cm * k * T / q) / (ΔT) = K3

In an eighth invention, the fifth to seventh inventions are described.
In one of the current switch circuits, the fourth node
Electrically connected between the node and the second potential node.
A constant current source having a positive temperature-dependent characteristic. No.
In the device of the ninth invention, any one of the devices of the fifth to the eighth devices is used.
In the current switch circuit, the fifth resistor and the sixth resistor
Is connected to the first power supply through a resistor or a diode.
Electrically connected to the second node. In the tenth invention,
The current switch circuit according to any one of the first to ninth inventions
At receiving light from the load and, accordingly,
The current flowing to the load is controlled.

In the eleventh invention, the fifth to tenth inventions
In the current switch circuit according to any one of the above,
Between the second Tr and the load and between the second Tr and the second
Between the potential nodes
Ninth and tenth Trs provided, and the third node
Between the node and the third Tr and the current response node.
A common power supply to the base between each of the fourth nodes
A source provided with an eleventh and a twelfth Tr.
5 and between the fifth Tr and the sixth resistor.
A power supply common to the base between the sixth Tr
Are provided, the 13th and 14th Trs are provided.

In the twelfth invention , the current switch of the second invention is provided.
In the switch circuit, the first Tr has a first electrode,
One end of which is electrically connected to the first potential node
A second electrode electrically connected to the other end of the load;
Electrically connected to the node. The second Tr
Has a first electrode electrically connected to the first potential node
And a second electrode is electrically connected to the second node.
Have been. Providing the first current to the current response node
Means that the first electrode is connected to the third electrode of the first Tr.
Is electrically connected, and the second electrode is connected to the first current control terminal.
Is electrically connected, and the third electrode is connected to the front through the first resistor.
The third Tr electrically connected to the second potential node
And a first electrode electrically connected to the current responsive node.
And a second electrode is electrically connected to the first current control terminal.
And a third electrode is connected to the second electrode through a second resistor.
A fourth Tr electrically connected to the second node;
A pole is electrically connected to a third electrode of the second Tr,
A second electrode is electrically connected to the first current control terminal.
And a third electrode is connected to the second potential node via a third resistor.
A fifth Tr electrically connected to the circuit.
Then, the third electrode of the first Tr and the third electrode of the second Tr
The third electrode is electrically connected via a resistor.

According to a thirteenth invention, in a current switch circuit such as a transmitter for optical communication, a first switch for switching a power supply current by turning on and off according to a potential difference between the first and second nodes.
And a second switch for supplying the power supply current to a load such as a light source, and a differential switch circuit electrically connected between the first and second Trs and a third node. First
And a second resistor, a first electrode is electrically connected to a first current control terminal, a second electrode is electrically connected to the third node, and a third electrode is A third Tr electrically connected to a current control terminal and a first electrode connected to the first Tr;
Is electrically connected to the current control terminal of
And a fourth Tr whose third electrode is electrically connected to the second current control terminal. Further, first and second load resistors respectively connected to a power supply, and a first load resistor to which a signal from a signal source is supplied.
An input terminal, a second input terminal to which a signal from a reference power supply or a reverse-phase signal source is supplied, a first electrode is electrically connected to the first input terminal, and a second electrode is is electrically connected to a load resistor of 1, the third electrode being electrically connected to said fourth node, a fifth Tr that Gyosu control the output voltage so as to supply to said first node A first electrode is connected to the second input terminal, a second electrode is electrically connected to the second load resistor, and a third electrode is electrically connected to the fourth node. And a sixth Tr for controlling output voltage to be supplied to the second node.

According to a fourteenth aspect , in the current switch circuit according to the thirteenth aspect , the current switch circuit is connected via the first and second nodes .
First and a second base resistor electrically connected to the first and second T r Te, the third and fourth T
First and second stabilizing resistors respectively connected between r and the second current control terminal are provided. Further, the output voltages of the fifth and sixth Trs are changed to the first and the second Trs.
A constant current is supplied to the seventh and eighth Trs for buffer and level shift transmitted to the first and second nodes via the second base resistor , respectively, and the seventh and eighth Trs, respectively. First and second constant current sources or first and second buffer resistors are provided.

[0019]

In the conventional current switch circuit, the differential switch circuit
Of the drive voltage for driving the first and second Trs constituting the path.
The width is constant. Switching by differential switch circuit
If the current value is small, the drive voltage of the differential switch circuit
Switching is possible even if the amplitude of the
As the switching current increases, the amplitude of the drive voltage increases.
If not, it will not switch. That is, switchon
Drive voltage amplitude required for(Potential difference)Is switching
Depends on current and temperature. However, conventional
In current switch circuits, large switching current
In addition, the amplitude of the drive voltage for driving the differential switch circuit is
bigValueI had to set it toIn this case, the drive power
For the pressure amplitude,When the switching current value is smallTo
IsThatThe drive voltage amplitude is too large, so the switch
The disadvantage is that large ringing occurs in the switching current.
Was.

In order to solve such inconvenience,
In the first to twelfth inventions, the first and second input terminals are provided.
Drive the potential applied to the third node and the load flowing through the third node
The third node based on the potential corresponding to the magnitude of the current
Potential having a potential difference corresponding to the magnitude of the current flowing through the
And generate the first and second via the first and second nodes.
2 Tr. In this way, the load is driven
Current flowing through the third node, the magnitude of the current value
Is generated and the first and second T
r. Therefore, the switching of the first and second Trs is performed.
Current at the load driving without reducing the switching speed.
The rate of ringing can also be kept below a certain level.

In the second invention, the electric current flowing to the third node is
Providing a first current proportional to the current to the current response node;
A first current flowing through the current response node;
Based on the potential applied to the input terminal of
A potential having a potential difference corresponding to the magnitude of the flowing current is
To the first and second Trs via the first and second nodes
Can be In a third invention, the first and second resistors are the first resistor.
And the internal emitter ohmic resistance of the second Tr itself
In the first and second Trs.
Controls the current dependence of the drive factor. here
And the drive factor is (drive factor) = Ln
(Ip (on) / Ip (off)). This dora
Faster switching speed with larger factor
However, ringing increases. Conversely, the drive factor
If switching is small, switching is slow but ringing is small.
It will be cheap.

In the fourth invention, the third and fourth Trs are mixed.
The first current flows from the fourth Tr to the current response
Output to the node. The third and fourth resistors set the mirror ratio
Set. In the fifth invention, the current response node is electrically connected.
Fifth and sixth Trs connected to the connected fourth node
As a result, the voltage corresponding to the magnitude of the current flowing through the third node
A potential having a difference is generated. In the sixth device, the seventh device
And the eighth Tr are the electric currents generated by the fifth and sixth Trs.
The potential difference is driven and applied to the first and second nodes. 7th
In the eighth invention, the values of K1, K2, and K3 can be set.
Vs. drive current vs. switching current and temperature
Control the dependence characteristics.

In the ninth invention, the fifth and sixth resistors are connected.
By the connected resistor or diode, the first Tr is saturated.
Sum is prevented. In the tenth invention, the output from the load is
The light that flows controls the current flowing through the load. No.
In the invention of No. 11, the ninth to fourteenth Trs are mirror current values.
The switching speed as well as the accuracy of
Works like that. In the twelfth invention, the third and fourth
The resistance connecting between the first electrodes of the Tr is the third and fourth resistances.
Works to prevent saturation of Tr.

In the current switch circuit of the thirteenth invention, the drive voltage levels of the first and second Trs, which are proportional to the switching current flowing through the differential switch circuit, are set to the fourth, fifth, and sixth levels.
And supplied to the first and second nodes. For example, when the fourth node has a positive temperature characteristic, the drive voltage levels of the first and second Trs corresponding to the temperature rise are generated in the fifth and sixth Trs. That is, when the switching current increases, the first Tr and the first Tr
The amplitude of the drive voltage of the second Tr increases. When the temperature rises, the positive temperature characteristic on the fourth node side causes
The amplitude of the drive voltage of the first and second Trs increases. As described above, the amplitudes of the output voltages of the fifth and sixth Trs that drive the differential switch circuit change to the optimum value according to the switching current value and the temperature, and the differential switch always changes at the optimum level. Circuit switching can be performed. As a result, a current switch with small ringing of the switching current and a high response speed can be performed even from a small switching current to a large switching current or even when the temperature changes.

In the fourteenth invention, the first and second base resistors and the first and second resistors of the thirteenth invention are the internal base resistance and the internal emitter ohmic resistance of the first and second Trs themselves. And controls the dependence of the drive factor of the first and second Trs on the switching current. That is, the switching current dependence coefficient of the drive factor can be set to + or-by selecting the first and second base resistors and the first and second resistors . Its Shi Te <br/>, when the drive factor is large, the switching is fast, the ringing is increased. Conversely, when the drive factor is small, switching is slow, but ringing is small. Further, the first and second stabilizing resistors are the third stabilizing resistor.
And the mirror current ratio constituted by the fourth Tr is stabilized .
It follows, it can solve the above problems.

[0026]

EXAMPLES First Embodiment FIG. 1 is a circuit diagram of a current switching circuit according to a first embodiment of the present invention. The current switch circuit is a circuit for driving a light source D of an LED or an LD, and has a first input terminal 11 to which a transmission signal source S is connected, a reverse-phase signal source r of the transmission signal source S, or the transmission signal source S S, the second input terminal 12 to which the reference power supply Vr corresponding to S is connected,
Current control terminals 21 and 22 and NPN first to eighth
Tr31-38. First and second Tr3
Reference numerals 1 and 32 constitute a differential switch circuit as differential switch means, third and fourth Trs 33 and 34 constitute a current mirror circuit, and fifth and sixth Trs 35 and 36 constitute a switch driver. The seventh and eighth Trs 37 and 38 have a buffer / level shift function.

A first base resistor 41 is connected between the node Na and the base of the first Tr 31 to be the first node N1.
Is connected between the node Nb and the base of the second Tr 32 that becomes the second node N2.
Is connected. The positive power supply + V on the first potential node Nv1 is connected to the collector of the first Tr 31 via the light source D, and the positive power supply + V is connected to the collector of the second Tr 32. Each emitter of the first and second Trs 31 and 32 is connected to the third emitter via the first and second resistors 51 and 52.
Are commonly connected to the node N3. Third node N3
Between the second current control terminal 22 and the third Tr 33
And the first stabilizing resistor 61 is a third resistor are connected in series, the current response is further connected to the fourth node N4 Roh
A fourth T is connected between the node Nc and the second current control terminal 22.
r34 and a second stabilizing resistor 62 as a fourth resistor are connected in series.

The third Tr 33 supplies the switching current Ip to the first and second Trs 31 and 32 forming the differential switch circuit, and the fourth Tr 34 forms the fifth and sixth Tr 35 forming the switch driver. , 36 through which a first current Ip / n proportional to the switching current Ip flows. The bases of the Trs 33 and 34 are commonly connected to the first current control terminal 21. The first and second stabilizing resistors 61 and 62 are resistors for stably operating the current mirror circuit, and include a third Tr33 and a fourth Tr34.
Can be omitted when the area ratio is close to 1.

A control voltage source is connected between the first and second current control terminals 21 and 22, or an appropriate DC voltage Vp is applied to the first current control terminal 21 and the second The control current source Ipc is connected to the current control terminal 22 to set the required switching current Ip. The first and second input terminals 11 and 12 are connected to respective bases of fifth and sixth Trs 35 and 36 constituting a switch driver,
The collectors of the Trs 35 and 36 are connected by fifth and sixth resistors .
They are connected to a positive power supply + V via certain first and second load resistors 71 and 72, respectively. Fifth and sixth Tr3
The emitters 5 and 36 are commonly connected to a fourth node N4, and supply a constant current Ic0 to the Trs 35 and 36 between the node N4 and the negative power supply -V on the second potential node Nv2. Current source Ic having a positive temperature-dependent characteristic is connected.

The collectors of the fifth and sixth Trs 35 and 36 have seventh and eighth Trs 3 for buffer and level shift.
7, 38 are connected to each other. This Tr37,
Reference numeral 38 denotes a transistor connecting the switch driver and the differential switch circuit. The collectors of Trs 37 and 38 are connected to the positive power supply + V, and the emitters are connected to the second and first nodes N2 and N1, respectively. . Between the second and first nodes N2 and N1 and the negative power supply -V, the first and second constant current sources IL1 for smoothly turning off the first and second Trs 31 and 32 are provided. , IL2 are connected to each other. The first and second constant current sources IL1, IL
2 may be replaced by a resistor. In this current switch circuit, a balanced input system is obtained by connecting the negative-phase signal source r to the second input terminal 12, and an unbalanced input system circuit is obtained by connecting the reference power supply Vr corresponding to the transmission signal source S. .

Next, the operation will be described. When the current switch circuit is provided in, for example, an optical communication transmitter, the optical communication transmitter includes Tr31 and Tr31 that constitute a differential switch circuit.
Even if a small current of about 1/100 or less of the ON operation side flows through the OFF operation side of 32, this does not pose a practical problem. T
The switching current Ip (on) flows when r31 is turned on, and the microcurrent Ip (of) is turned off when Tr32 is barely turned off.
f) is flowing. Tr collector current Ic
c, if the base-emitter voltage Vbe, Is the reverse saturation current of the Tr, the electron charge q, Boltzmann constants k, absolute temperature is T, can be approximated by the following equation (1). Icc = Is * exp (q * Vbe / k / T) (1) where *: multiplication

The common emitter current gain of Tr is HFE,
Rc = fifth resistor 71 = sixth resistor 72, Re = first resistor 51 = second resistor 52, Rb = first base resistor 4
1 = second base resistor 42, Ip (on) >> Ip (of
f), (and on), m = Ln (Ip (on) Ip ≒ Ip / Ip (off)) ··· (2) However, Ln (); and put the natural logarithm, node N a, N
The potential difference V12 between b is expressed as follows: V12 = Ip * (Re + Rb / (1 + HFE)) + m * k * T / q (3)

K * T / q ≒ 26 mV, Ip (on) / I
Assuming that p (off) = 100 to 1000, the value of (m * k * T / q) in the equation (3) is about 120 mV to 180.
mV. Ip (on) / Ip (off) = 1000
Even at 0, it is about 240 mV. Third and fourth Tr3
In the current mirror circuit composed of the third and third stabilizing resistors 61 and 62, when the area ratio between Tr33 and Tr34 and the resistance ratio between the stabilizing resistors 61 and 62 are set as follows, n = (Emitter area ratio of Tr33) / (Emitter area ratio of Tr34) = Stabilizing resistor 62 / Stabilizing resistor 61 (4) If switching current Ip flows through Tr33, Tr34
Is (Ip / n). Therefore, Tr3
Current I flowing through the switch driver composed of
co is expressed by the following equation (5).

Ico = Ic + Ip / n (5) Further, the output amplitude voltage V0 of the switch driver composed of the Trs 35 and 36 is as follows: V0 = Rc * Ico = Rc * (Ic + Ip / n) (6) ). From the circuit operation, the output amplitude voltage V0 and the first and second
Are equal to the voltage V12 between the nodes N1 and N2, the following equations (7) and (8) hold.

V0−V12 ≒ 0 (7) V0−V12 = Rc * (Ic + Ip / n) −Ip * (Re + Rb / (1 + HFE)) − m * k * T / q = Ip * (Rc / n -Re-Rb / (1 + HFE)) + (Rc * Ic-m * k * T / q) (8) If the first term of equation (8) is "≒ 0" independently, then Ip is Even if it changes, m is not affected. With m as a constant value, (8)
If the second term in the equation is independently “≒ 0”, then m will not be affected even if the temperature changes. If both the first term and the second term are “≒ 0”, m can be kept constant with respect to the change in Ip and the temperature change. These relationships are shown in the following equations (9) to (11).

Rc / n-Re-Rb / (1 + HFE) ≒ 0 (9) (1st item ≒ 0) Rc * Ic-m * k * T / q ≒ 0 (10) (normal temperature (Rc * Ic−m * k * T / q) / (ΔT) ≒ 0 That is, Δ (Rc * Ic) / (ΔT) −m * k / q ≒ 0 (second Term temperature odor {0) ... (11) Add the values of the internal base resistance and internal emitter ohmic resistance of Tr31 and Tr32 to Rb and Re, respectively, and (9)
If Expressions (11) are satisfied, the ideal shape is obtained. The absolute value of (m * k / q) in equation (11) is about 0.5 mV / ° C.,
Constant current source Ic with the same temperature scent of (Rc * Ic)
Can be easily realized by combining a band gap power supply with a transistor and the like.

As is apparent from equations (7) and (8), m is given by (8) with respect to changes in Ip, Ic, T and the like.
The value of the expression changes to a value that is zero. By making equation (9), which is a component of the first term in equation (8), a plus, it is possible to increase m as Ip increases. If Rc, Rb, and Re, which are external resistors, are set to be somewhat large,
The base resistance and the emitter ohmic resistance inside the Tr can be neglected. By appropriately setting the temperature coefficient of the constant current source Ic, m can be appropriately changed with respect to the temperature. As described above, by freely setting the values of the expressions (9) to (11), the switch drive factor with respect to Ip and temperature change can be controlled (control of the m value).

The first embodiment has the following advantages. A current switch with small ringing can be always realized over a wide range of switching currents Ip from a small switching current Ip to a large switching current Ip. For example, when FIG. 2 of the related art and FIG. 1 of the first embodiment are configured with the same element and a simulation comparison is performed,
In order to suppress the ringing amount of p to 15% or less of the steady state Ip, the conventional circuit of FIG.
x) to Ip (max) / 2, whereas in the circuit of FIG. 1 of the present embodiment, Ip (max) to Ip (max) / 20
And the variable range of about one digit Ip is widened.

Therefore, the current switch circuit of this embodiment is
For example, when used for an LED driver or LD driver of optical communication, the optical waveform of the transmitter becomes good, so that stable automatic power control of the transmitter and high-quality reception with a small error rate can be realized. Furthermore, since the signal pulse width can be reduced to just before the time when the ringing converges,
A high-speed optical transmitter can be realized. In addition, various LD and L
High versatility (switching current I
(a range of p is wide). 5 to 8
2 is a circuit diagram of a current switch circuit according to second to fifth embodiments of the present invention.

Second Embodiment In the current switch circuit shown in FIG. 5, a resistor 73 for level shift is added so as to be able to cope with the light source D having a large voltage drop when turned on. The level of the emitter potential is shifted. The first and second constant current sources IL1 and IL2 of the buffer Trs 37 and 38 are replaced with first and second buffer resistors 81 and 82, respectively. Then, a DC bias source Ib is added to the light source D, and the third and fourth TRs 33,
The switching current Ip is controlled by the first current control terminal 21 on the base side of 34. With such a configuration, the level shift resistor 73 can prevent the first Tr 31 from being saturated or the like, and can perform an accurate current switch.

Third Embodiment In the current switch circuit of FIG. 6, a level shift is performed by using a diode 74 instead of the resistor 73 in the current switch circuit of FIG. A constant current source IL is added to the buffer resistors 81 and 82 to form a hybrid circuit. A resistor 63 is added between the second current control terminal 22 and the negative power supply -V. Then, a part of the light output of the light source D constituted by the LD is converted to a back light detector 90 such as a light receiving diode (hereinafter referred to as PD).
And an auto power control circuit 91 for controlling the switching current Ip and the output current Ib of the collector of the Tr31. With such a configuration,
As in FIG. 5, an accurate current switch can be performed, and an auto power control circuit 91 is added.
The fluctuation of the light source D can be controlled.

Fourth Embodiment In the current switch circuit of FIG. 7, a resistor 63 is connected between the second current control terminal 22 and the negative power source -V in the current switch circuit of FIG. Control is performed at the first current control terminal 21. Seventh and eighth Tr37,
Level shift is performed by adding buffer resistors 81 and 82 to each of the 38 emitters. The ninth and tenth Trs 101 and 102 to which the power supply Vd1 is commonly connected to the base are connected to the first and second Trs 101 and 102.
Of the eleventh and twelfth transistors connected in series to the collectors of the Trs 31 and 32 of FIG .
r103 and 104 are connected in series to the third and fourth nodes N3 and N4, respectively, and the thirteenth and fourteenth Trs 105 and 106 whose bases are commonly connected to the power supply Vd2 are connected to the fifth and sixth Trs 35 and 36. Connected in series to the collector side. With such a configuration, it is possible to improve the accuracy of the mirror current value and the switching speed.

Fifth Embodiment In the current switch circuit shown in FIG. 8, in the current switch circuit shown in FIG. 1, the first and second constant current sources IL1 and IL2 are replaced with the first and second base resistors 81 and 82. The level shift is performed by replacing the hybrid circuit with the constant current source IL and adding diodes 111 and 112 to the emitters of the seventh and eighth Trs 37 and 38, respectively. A resistor 63 is provided between the second current control terminal 22 and the negative power supply -V, and the switching current Ip is controlled by the first current control terminal 21. And FIG.
Circuit replacement as shown in (a) and (b) is performed.

That is, FIGS. 9A and 9B are partial circuit diagrams in FIG. As shown in FIG. 9A, the resistance 5 of FIG.
As shown in FIG. 9 (b), a T-shaped circuit composed of the first, second and first transistors 52, 61 and Tr33 is connected to first and second resistors 51 and 52 .
3 and the third and fifth Tr3s 61-1 and 61-2.
3-1 and 33-2 are replaced with a π-type circuit ,
Mirror movement in combination with the second resistor 62 and the second Tr 34
I try to make it. The resistances of the resistors 51 and 52 are equal, and the resistors 61-1 and 61-2 have twice the resistance of the resistor 61. Also, the emitter size of Tr33 is set to A3
Then, the emitter sizes of Trs 33-1 and 33-2 are set to A3 / 2. With such a configuration, no DC current flows through the resistors 51 and 52, so that the Tr3
There are advantages that saturation of 3-1 and Tr33-2 can be prevented.

The present invention is not limited to the above embodiment,
Various modifications are possible. For example, in the current switch circuits of the first to fifth embodiments, NPN-type Trs are used.
r. When a PNP Tr is used, the voltage and current, the polarity of the connection diode, and the like may be inverted. The automatic power control circuit 91 of FIG. 6 in the third embodiment can be provided in another embodiment. Further, the above embodiment can be applied to loads other than the light source.

[0046]

[Effects of the Invention] As described in detail above, the first to the first
According to the second aspect of the present invention, the first and second input terminals
Potential and the current driving the load flowing to the third node are large.
Flows to the third node based on the potential corresponding to the magnitude
Generating a potential having a potential difference corresponding to the magnitude of the current,
The first and second Trs constituting the differential switch
And via the second node. That
Therefore, the current for driving the load flows to the third node,
Potential difference applied to the first and second input terminals greatly,
When the current has a large current value, a large current value corresponding to the current value is obtained.
A large potential difference is applied to the first and second Trs. Yo
Therefore, the switching speed of the first and second Trs does not decrease.
No. In addition, since the current flowing through the load is large,
The rate of ringing does not increase. Meanwhile, the third
If the current flowing through the node is small,
Since the potential difference given to the first and second Trs is small,
Even if the current driving the load is small, the rate of ringing is small.
Does not grow. In this case, the power to drive the load is
Since the current is small, the potential given to the first and second Trs
Smaller difference reduces first and second switching speeds
do not do. Therefore, regardless of the magnitude of the current driving the load,
The transient response characteristics of the output amplitude of the load such as LED and LD.
Without reducing the current in driving the load.
The ratio of the ringing current can be kept below a certain value. Therefore, various
Versatility to drive the light source of
Reliability can be improved.

According to the thirteenth invention, a current switch with small ringing can be always performed over a wide range of output current from a small output current to a large output current. Since the ringing level can be reduced, the signal pulse width can also be reduced to just before the ringing convergence time, and the operating speed can be increased. Since ringing can be reduced over a wide output current range, the versatility for driving various light sources is expanded. According to the fourteenth invention , since the first and second stabilizing resistors are provided, the third and fourth Trs can be operated stably. Moreover, the first and second
Of the constant current source or the first and second buffer resistors
For example, the off operation of the Tr and the second Tr can be smoothly operated.

[Brief description of the drawings]

1 is a circuit diagram of a current switching circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional current switch circuit.

FIG. 3 is a circuit diagram of a conventional current switch circuit.

FIG. 4 is a waveform diagram of the switching current Ip of FIG. 2;

5 is a circuit diagram of a current switching circuit according to a second embodiment of the present invention.

6 is a circuit diagram of a current switching circuit according to a third embodiment of the present invention.

7 is a circuit diagram of a current switching circuit according to a fourth embodiment of the present invention.

8 is a circuit diagram of a current switching circuit according to a fifth embodiment of the present invention.

FIG. 9 is a partial circuit diagram in FIGS. 1 and 8;

[Explanation of symbols]

11, 12 First and second input terminals 21, 22 First and second current control terminals 31 to 38 First to eighth Trs 41, 42 Base resistors 51, 52, 61 , 62 First, second , Third and fourth resistors 71, 72, first and second load resistors IL1, IL2 first and second constant current sources Ip switching current Ipc control current source D light source + V positive power source -V negative power source N1 to N4 First to fourth nodes Nc Current response nodes Nv1 and Nv2 First and second potential nodes

Claims (14)

(57) [Scope of request for utility model registration] 1. A first node and a second node, respectively.
The conduction state is controlled according to the applied potential, and the first
A first potential node to which the potential of
A third electrically connected to the applied second potential node
Electrically and in parallel with each other
Having a first transistor and a second transistor,
Between the first potential node and the third node,
The current flowing through a load connected in series with the first transistor
Differential switch means for controlling the flow rate, Provided to a first input terminal and a second input terminal, respectively.
Depending on the potential of the third node and the current flowing through the third node.
The first and second nodes flow to the third node
Apply a potential having a potential difference of a magnitude corresponding to the magnitude of the current
A current switch circuit, comprising: 2. The magnitude of a current flowing through the third node
Means for giving a potential having a potential difference of a magnitude according to A magnitude proportional to the magnitude of the current flowing through the third node;
Means for providing a first current to a current responsive node; The first input node electrically connected to the current response node;
Power terminal and the second input terminal, respectively.
The first node and the first node depending on the position and the first current.
The second node has a magnitude corresponding to the magnitude of the first current.
Means for applying a potential having a potential difference of
The current switch circuit according to claim 1, wherein: 3. The first transistor has a first electrode.
Is electrically connected to the first potential node via the load.
A second electrode is electrically connected to the first node
And a third electrode is connected to the third node via a first resistor.
Electrically connected to the The second transistor has a first electrode connected to the first electrode.
Electrically connected to the first potential node to which the potential is applied.
And a second electrode is electrically connected to the second node. Connected
And a third electrode is connected to the third node via a second resistor.
Or electrically connected to the
2. The current switch circuit according to 2. 4. The method according to claim 1, wherein the first current is supplied to the current response node.
The means for providing is such that the first electrode is electrically connected to the third node.
And the second electrode is connected to a third electrode to which a predetermined potential is applied.
And the third electrode is electrically connected to the first current control terminal.
A third transistor connected to one end of the third resistor;
One electrode is electrically connected to the current responsive node;
Two electrodes are electrically connected to the first current control terminal.
And a fourth electrode in which a third electrode is connected to one end of a fourth resistor.
A transistor, and the other ends of the third and fourth resistors are
Being electrically connected to the second potential node.
The current switch circuit according to claim 2, wherein 5. A magnitude corresponding to the magnitude of the first current
The first electrode is connected to the first electrode through a fifth resistor.
And electrically connected to the first potential node,
The electrode is a first input terminal to which a signal from a signal source is provided.
And a third electrode is connected to the current responsive node.
Electrically connected to a fourth node electrically connected to the node.
A fifth transistor and a first electrode are connected to a sixth resistor.
Is electrically connected to the first potential node through
2 electrodes are connected to a reference power source or a negative-phase signal source.
Electrically connected to a second input terminal to which a signal is applied;
A third electrode is electrically connected to the fourth node
And a sixth transistor, wherein the first or second input is provided.
According to the relationship between the levels of the potentials applied to the force terminals, the first
And the relationship between the levels of the potentials applied to the second node is determined.
3. The current switch according to claim 2, wherein
Switch circuit. 6. A first electrode is connected to the first potential node.
Pneumatically connected and the second electrode is connected to the fifth transistor.
The fifth electrode between the first electrode and the fifth resistor.
Electrically connected to the first electrode and the fifth resistor of the transistor;
And a third electrode is connected to the second node via a seventh resistor.
And electrically connected to the second potential node.
A seventh transistor connected to electricity; A first electrode electrically connected to the first potential node;
And the second electrode is the first electrode of the sixth transistor.
And between the sixth resistor and the sixth resistor.
Electrically connected to the first electrode and the sixth resistor,
The third electrode is the eighth An electrical connection to the first node via a resistor
And electrically connected to the second potential node.
Having an eighth transistor connected thereto.
The current switch circuit according to claim 5. 7. The conduction of the first and second transistors
The current at the time of non-conduction and the current at the time of non-conduction are IP (on) and IP
(Off), the charge of the electron is q, and the Boltzmann constant is
k, the absolute temperature is T, and the third transistor is a bipolar transistor.
Transistor of the third transistor.
And the fourth transistor is bipolar.
Transistor, and an emitter of the fourth transistor.
The area of the transistor is A4, and the emitter
When the flow amplification factor is HFE, K1, K
2. By setting the value of K3, the drive factor m
Controlling the dependence on current and temperature
The current switch circuit according to claim 6, wherein: n = A
3 / A4 = fourth resistance / third resistance IP (on) >> IP (off), IP = IP (on) m = Ln (IP (on) / IP (off)) (However, Ln (); natural logarithm) Rc = fifth resistance = sixth resistance, Re = first resistance = first resistance
2 resistance, Rb = seventh resistance = eighth resistance (Rb / n-Re-Rb / (1 + HFE)) = K1 Rc * cm * k * T / q = K2 (However, *; multiplication) Δ (Rc * cm * k * T / q) / (ΔT) = K3 8. The fourth node and the second potential node
Has a positive temperature-dependent characteristic electrically connected to the
9. A constant current source according to claim 5,
The current switch circuit according to any one of the above. 9. The fifth resistor and the sixth resistor,
To the first potential node via a resistor or a diode
9. The method according to claim 5, which is electrically connected.
The current switch circuit according to any one of the above. 10. Receiving light from said load and responding to it.
Flow to the load To control the current flowing
The electronic device according to any one of claims 1 to 9, wherein
Current switch circuit. 11. The first transistor and the load,
Between the second transistor and the second potential node.
And a common power supply to each base
Ninth and tenth transistors, Between the third node and the third transistor and
Between the current response node and the fourth node,
Eleventh and twelfth where a common power supply is applied to each base
Having a transistor of Between and before the fifth resistor and the fifth transistor
A sixth resistor between the sixth resistor and the sixth transistor;
Thirteenth and fourteenth power supplies are supplied to the bases in common.
5. The transistor according to claim 5, wherein
11. The current switch circuit according to any one of 10. 12. The first transistor according to claim 1, wherein:
A pole is electrically connected at one end to the first potential node
The second electrode is electrically connected to the other end of the load
Electrically connected to the first node; The second transistor has a first electrode connected to the first electrode.
And a second electrode electrically connected to the second node.
Electrically connected to the node, Means for providing the first current to the current response node,
A first electrode is connected to a third electrode of the first transistor.
And the second electrode is electrically connected to the first current control terminal.
And a third electrode is connected via a first resistor.
A third transistor electrically connected to the second potential node
And a first electrode electrically connected to the current responsive node.
A second electrode is electrically connected to the first current control terminal.
And a third electrode is connected to the second electrode via a second resistor.
Transistor electrically connected to the potential node of
And a first electrode is a third electrode of the second transistor.
And the second electrode is electrically connected to the first current control.
Electrically connected to the terminal, and the third electrode is connected through a third resistor.
And a fifth potential node electrically connected to the second potential node.
Having a transistor and A third electrode of the first transistor and a second transistor
The third electrode of the star is electrically connected to the third electrode via a resistor.
3. The current switch according to claim 2, wherein Switch. 13. According to a potential difference between a first node and a second node.
First and second switching power supply currents by turning on and off
Transistors for supplying the power supply current to the load.
Dynamic switch circuit, Between the first and second transistors and a third node
A first and a second resistor respectively electrically connected to A first electrode is electrically connected to the first current control terminal;
A second electrode is electrically connected to the third node;
The third electrode is electrically connected to the second current control terminal.
Three transistors, A first electrode is electrically connected to the first current control terminal.
A second electrode is electrically connected to the fourth node,
Three electrodes are electrically connected to the second current control terminal.
A fourth transistor; First and second load resistors respectively connected to a power supply;
A first input terminal to which a signal from a signal source is provided; Given a signal from a reference power supply or
A second input terminal, A first electrode is electrically connected to the first input terminal;
A second electrode is electrically connected to the first load resistor;
A third electrode is electrically connected to the fourth node, and
Controlling the supply voltage to be supplied to the first node;
5 transistors, A first electrode is connected to the second input terminal and a second electrode
A pole is electrically connected to the second load resistor and a third
A pole is electrically connected to the fourth node to reduce an output voltage.
A sixth truck controlling to supply to the second node
Current switch circuit having a transistor
Road. 14. The current switch circuit according to claim 1,
And The first and second nodes via the first and second nodes
A first and a second, respectively, electrically connected to the transistor;
Two base resistors, The third and fourth transistors and the second current control
First and second terminals electrically connected between the first and second terminals, respectively.
And the stabilizing resistance of The output voltages of the fifth and sixth transistors are set to the first
And the first and second nodes via a second base resistor.
7th for buffer and level shift to be transmitted to each
And an eighth transistor; A constant current is supplied to the seventh and eighth transistors, respectively.
The first and second constant current sources or the first and second
Current switch circuit characterized by providing a
Road.