JPH02131002A - Bias power supply circuit - Google Patents

Abstract

PURPOSE:To give a desired temperature characteristic in response to the temperature characteristic of a semiconductor element to a bias voltage by providing a PNP transistor(TR) for giving the temperature characteristic whose base is connected to a middle point of a voltage division resistor, whose collector is connected to ground and whose emitter is connected to a power supply and providing an output terminal which is connected to the emitter side of the NPN TR, from which a bias voltage is outputted. CONSTITUTION:A connecting point of voltage division resistors 32, 34 is connected to a base of a PNP TR 36. Then the collector of the PNP TR 36 is connected to ground and the emitter is connected to a power supply VCC via a diode 38 and a resistor 40. Then a bias voltage VREF is outputted from a connecting point between the resistor 40 and the diode 38. Then the outputted bias voltage VREF depends on the voltage drop VF of the PNP TR 36 and diodes 30, 38. Thus, the bias voltage VREF is fluctuated in response to the temperature dependency circuit of the VF of the temperature elements.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bias power supply that supplies a predetermined bias voltage, particularly one having predetermined temperature-dependent characteristics.

[Prior Art] There are many cases in which a predetermined bias voltage is required in an integrated circuit such as an IC. In such a case, the simplest method is to use resistance division. That is, this is a method in which two resistors are connected in series between a power supply and ground, and a predetermined voltage is output from the midpoint of the resistors, thereby dividing the power supply voltage and outputting it as a bias voltage. According to this method, a desired bias voltage can be obtained according to the ratio of the resistance values of the two resistors.

However, in this resistance division method, when the power supply voltage fluctuates, the bias voltage follows the fluctuation. In circuits that require a bias voltage, the value of the bias voltage often has a large effect on its characteristics, and there is a desire to minimize fluctuations.

Therefore, various constant voltage circuits are used.

Among these, bandgap constant voltage circuits are widely used as constant voltage sources because they can supply a constant voltage and have substantially zero temperature dependence.

Additionally, a Zener diode that conducts at a predetermined breakdown voltage or higher is also used as a constant voltage source, but since the breakdown voltage of this Zener diode is usually relatively high, about 5 to 6V, it cannot be used when the power supply voltage is relatively high. It's being used. Note that since the Zener diode has temperature-dependent characteristics, the output voltage will depend on temperature changes if left as is. Therefore, diodes are often connected in series to cancel out the temperature dependence characteristics.

Examples of these constant voltage circuits are shown in Figures 3 (A) and (B).
, shown in (C). FIG. 3(A) shows an example of a constant voltage circuit using resistance division, FIG. 3(B) shows an example of a bandgap constant voltage circuit, and FIG. 3(C) shows an example of a constant voltage circuit using a Zener diode.

[Problem to be solved by the invention] As described above, various constant voltage circuits have been proposed in the past,
It's being used. As mentioned above, in normal cases, it is often desirable to have no temperature-dependent characteristics.

However, depending on the circuit that requires a bias voltage, it may be desirable to have a predetermined temperature-dependent characteristic. In particular, in integrated circuits such as ICs, the circuits are often formed of semiconductor elements, and therefore the circuits themselves operate according to voltages that vary depending on temperature. Therefore, it is better that the voltage supplied here also have similar temperature dependent characteristics.

For example, in a constant current circuit as shown in FIG. 4, it is preferable that the voltage vREF of the bias source has a predetermined temperature dependence characteristic.

That is, in this circuit, a current mirror made up of transistors Q1 and Q2 causes the same current flowing to the transistor Q1 side to flow to the transistor RO2 side, and causes a constant current to flow out from the electric circuit Ci.

The current I in this circuit is I-(V-2-V)/(R1+R2)TEREF
P is represented. Here, ■ is the voltage between the base and emitter of the transistors Q1 and Q2.

And the transistor is usually -1,8m V/'C
It has certain temperature-dependent characteristics. The base-emitter voltage Vp of the transistor is about 0.7 to 0.8V,
Since the voltage change due to a temperature change of 50° C. is 0.09V, the change in the φ current ■ due to this temperature change becomes quite large. And transistors Q1, Q2
2 of the voltage change ΔvP based on the respective temperature-dependent characteristics of
The current {circle over (2)} flowing out from the electric circuit Ci changes according to the multiplication (2·Vp). In such a case, it is also possible to give the bias voltage ■ a temperature characteristic that cancels the temperature dependence characteristics of the transistors Q1 and Q2.
FIG. 4 shows an example of the configuration of a differential amplifier. In this example, the input signal IN is supplied to the bases of a pair of differential amplification transistors Q6 and Q7 via transistors Q4 and Q5 forming an emitter follower. The potential at the connection point of the constant current source IO is the differential amplification transistor Q4, Q5, Q.
6.Q7 It depends on the temperature characteristics.

Constant current source I. Although a constant current flows regardless of changes in the potential on the upstream side, it is preferable that the potential on the upstream side does not fluctuate. In particular, if the potential on the upstream side becomes less than a predetermined constant voltage, the constant voltage circuit may not function sufficiently. In many cases, the bias voltage VRFP must be suppressed to a fairly low level due to the relationship with the power supply voltage.
, Q6, and Q7 are desired to have temperature-dependent characteristics that cancel them.

It is desired that

Purpose of the Invention The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a bias power supply circuit that supplies a bias voltage having predetermined temperature-dependent characteristics.

[Means for Solving the Problem] In order to achieve the above object, a bias power supply circuit according to the present invention applies a predetermined bias voltage to an electric circuit having a semiconductor element provided on the same substrate of an integrated circuit. In the bias voltage circuit to be supplied, a constant voltage circuit outputting a constant voltage having substantially no temperature dependence characteristics, a voltage dividing resistor connected to the output side of the constant voltage circuit and consisting of two resistors connected in series; A PNP type transistor for providing temperature characteristics, whose base is connected to the midpoint of this voltage dividing resistor, a collector connected to ground, and an emitter connected to a power supply, is connected to the emitter side of the above PNP type transistor, and a bias voltage and an output terminal for outputting a bias voltage having desired temperature-dependent characteristics to an electric circuit on the same substrate.

[Operation] A constant voltage having no substantial temperature-dependent characteristics is converted into a predetermined voltage by a voltage dividing resistor, and is supplied to a PNP type transistor for imparting temperature characteristics. A bias voltage is output from the emitter side of this PNP transistor. Therefore, the output bias voltage is set to a predetermined voltage by the voltage dividing resistor, and is given the temperature characteristics required in an electric circuit on the same substrate corresponding to a PNP transistor. Further, since a PNP type transistor is employed, unnecessary current does not flow into the voltage dividing resistor, and a predetermined bias voltage can be output.

Note that if a diode or the like is further added to this circuit, the temperature dependence characteristics can be changed.

[Example] Hereinafter, a bias power supply circuit of the present invention will be described based on the drawings.

FIG. 1 is a circuit diagram showing a bias power supply circuit according to an embodiment of the present invention.

The bandgap constant voltage circuit 10, which is a constant voltage source with substantially no temperature dependence characteristics, has a constant voltage V. Outputs 0. The output side of this bandgap constant voltage circuit 10 is connected to the base of a transistor 12. The emitter of this transistor 12 and the emitter of a transistor 14 arranged opposite to each other are connected to ground via a constant current source 16. These transistors 12.
The collector of 14 is connected to the power supply V through transistors 18 and 20 forming a current mirror. Connected to 0.

The base of the transistor 14 is connected via a capacitor 22 to the base of a transistor 24, whose collector is connected to the power supply Vcc and its emitter is connected to ground via two series-connected resistors 26 and 28. Then, the connection point between the collectors of the transistors 20 and 14, the base of the transistor 24, and the capacitor 2
The connection points of the resistors 26 and 28 are connected, and the connection points of the transistor 14 and the capacitor 22 are also connected.

The connection point between the transistor 24 and the resistor 26 outputs a voltage Vo, and the anode of a diode 30 is connected to this connection point. There is.

The connection point of the voltage dividing resistors 32 and 34 is connected to the base of a PNP transistor 36, whose collector is grounded and whose emitter is connected to the power supply V via a diode 38 and a resistor 40. Connected to 0. A bias voltage VREF is output from between the resistor 40 and the diode 38.

In such a circuit, the bandgap constant voltage circuit 1
From 0 is the power supply voltage ■. A predetermined constant voltage V that does not vary with zero fluctuations and temperature changes. 0 is output. This constant voltage voo is determined by the transistors, resistors, etc. that make up the bandgap constant current detour, but in order to eliminate the temperature dependence characteristics, a certain combination of these must be used. , the output voltage V. 0 is 1
．． It is limited to about 2V.

This constant voltage Voo is a voltage V that is increased after being subjected to a predetermined boosting action. The output will be closed.

Transistor 12 has a constant voltage V. A constant current flows through the zero current, and correspondingly the same current flows through the transistor 18, 20 forming a current mirror arranged on the one current side.

The sum of the current flowing through the transistor 14 and the current flowing through the transistor 12 is kept constant by the constant current source 16. Here, the collector side of the transistor 20 is connected to the base of the transistor 24, and the potentials thereof are equal. Furthermore, the base potential of the transistor 14 is
It is connected to the midpoint between the resistors 26 and 28 and held at this potential.

Therefore, the voltage V at the connection point depends on the ratio of the magnitudes of the resistors 26 and 28. can be determined. And this voltage V. is the power supply voltage V. C, but can be a predetermined high voltage.

Next, a voltage dividing resistor 3 is connected to the connection point via a diode 30.
2.34 are connected and depending on these values, PN
A predetermined voltage (1) is supplied to the base of the P-type transistor. That is, this voltage v1 is as follows depending on the voltage drop V of the diode 30 and the resistance values R32 and R34 of the resistor 32.34.

V = (Vo-VF)・R34 / (R32+R34) For example, vo is 4V, VF is 0.75V, R32 and R3
If the resistance values of 4 are the same, Vt is 1.625
It becomes V.

Then, the base potential of the PNP transistor 36 is vl
Therefore, the voltage obtained by adding the pace emitter voltage Vp of the PNP transistor 36 and the voltage drop Vp of the diode 38 to this voltage is output as the bias voltage REF.

Here, a characteristic feature of this embodiment is that the output bias voltage vREF corresponds to the Vp of the PNP transistor 36 and the diode 30.38. Therefore, the bias voltage Vya is Vl of these semiconductor elements.

It will fluctuate depending on the temperature-dependent characteristics of

In other words, V REP ″V t + 2 V p, and since vl includes Vp as mentioned above, the resistance is 32.3
When the resistance value of 4 is 1:1, the bias voltage VREP
It corresponds to 1.5VF. Therefore, this 1
．． A temperature characteristic corresponding to 5VF is given to the bias voltage vREP. And such temperature characteristics are
Depending on the number of diodes 30, 3B to be inserted, etc.
It can be adjusted arbitrarily.

Also, by adjusting the value of resistor 32.34, Vl
can be adjusted arbitrarily, so the bias voltage VREF can be set to a desired value. Note that in normal cases, if the diode 3o is omitted, the temperature characteristics will not change due to the resistors 32 and 34, so it is omitted.
It is preferable to adjust the temperature characteristics depending on the number of diodes 38.

Here, in the above description, the diode 30.38
, the Vp of the transistor 36 is described as the same value.

This is because in an integrated circuit, these semiconductor elements are formed on the same substrate, and unless their specifications differ greatly, they will have the same value.

Other circuits that require a bias voltage formed on the same substrate also have similar semiconductor elements, and their required temperature characteristics often also correspond to the same VF. Therefore, by increasing or decreasing the number of diodes 38 connected in series, it is possible to meet the demands for providing temperature characteristics in many cases.

Note that the diode on such an integrated circuit often uses a transistor whose base and collector are short-circuited, and the voltage drop between the emitter and the base is usually the voltage drop.

Furthermore, the reason why a PNP type transistor is adopted as the transistor 36 is that the current flowing from the diode 38 is connected to the resistor 34.
This is to prevent it from flowing into the

In other words, if a PNP type transistor is used, the resistance 3
4 can be suppressed to just the base current or to a predetermined small current, and the desired bias voltage VREP
You can get

What is shown in FIG. 2 is a modification of the bias voltage output section. In this example, a diode 50 is connected to the emitter side of the PNP transistor 36 in addition to the diode 38.
is located. Therefore, the voltage at point C on the upstream side of this diode 50 corresponds to the voltage drop of 3VF across the PNP transistor 36 and the diode 38.50.

Therefore, the voltage at this point C has temperature dependent characteristics corresponding to 3VF.

However, this point C is connected to the base of a transistor 52 forming an emitter follower, the collector of this transistor 52 is connected to the power supply Vcc, the emitter is grounded via a constant current source 54, and the upstream side of this constant current source A bias power supply VREF is taken out from the side. Therefore, the bias voltage VREP is the potential at point C minus Vp of the transistor 52.

Therefore, the bias voltage VREP in this example is 2■,
It is given a temperature characteristic according to the temperature.

Note that by adding an emitter follower in this way, the current supply capability of the bias power supply VREP can be increased, and this is particularly suitable when it is desired to increase the current supply.

Furthermore, a plurality of such circuits can be connected to the dots in FIG. By connecting a plurality of them, it is possible to obtain a bias power supply having a plurality of types of temperature characteristics, and it is possible to supply a desired bias voltage having desired temperature characteristics to a plurality of electric circuits.

Further, the bias circuit according to the present invention is not limited to the above-mentioned example, but can be suitably applied to any circuit that requires a constant voltage source having temperature characteristics.

Further, as a constant voltage circuit having substantially no temperature characteristics, a circuit using a Zener diode shown in FIG. 3(C) or the like may be employed.

[Effects of the Invention] As described above, according to the bias circuit according to the present invention, it is possible to set the bias power supply to a desired voltage and to give it desired temperature-dependent characteristics. Therefore, it is possible to give the bias voltage a desired temperature characteristic corresponding to the temperature characteristic of the semiconductor element required in the electric circuit on the same integrated circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a bias power supply circuit according to one embodiment of the present invention, FIG. 2 is a circuit diagram showing another embodiment, FIG. 3 is a circuit diagram showing a constant voltage circuit, FIGS. FIG. 5 is a circuit diagram showing an example of an electric circuit that requires temperature characteristics. 10... Bandgap constant voltage circuit 32.34
... Voltage dividing resistor 36 ... PNP type transistor

Claims (1)

[Claims] A bias voltage circuit that supplies a predetermined bias voltage to an electric circuit having semiconductor elements provided on the same substrate of an integrated circuit, which outputs a constant voltage that has substantially no temperature dependence characteristics. A constant voltage circuit, and two connected in series connected to the output side of this constant voltage circuit.
a PNP type transistor for imparting temperature characteristics, the base of which is connected to the midpoint of the voltage dividing resistor, the collector connected to ground, and the emitter connected to a power supply; and the above PNP type transistor. A bias power supply circuit comprising: an output terminal connected to the emitter side of the circuit and outputting a bias voltage, and supplying a bias voltage having desired temperature-dependent characteristics to an electric circuit on the same substrate.