JPH053933B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a Schmitt trigger type triangular wave oscillation circuit used, for example, as a one-terminal type integrated circuit oscillation circuit.

[Technical background of the invention]

FIG. 3 shows a conventional one-terminal type triangular wave oscillation circuit implemented as an integrated circuit (IC), which includes differential pair transistors Q ₁ and Q ₂ for differential amplification type voltage comparison,
A current mirror circuit 31 includes an input transistor Q ₃ driven by the collector current of the transistor Q ₁ and first and second output transistors Q ₄ and Q ₅ , and a constant voltage from an external constant voltage source 32.
A series resistor connected between the constant voltage terminal 33 to which V _r is applied and the base of the transistor Q ₁
The output of the first output transistor Q 4 of the current mirror circuit 31 is connected between the interconnection point of R ₁ and R ₂ and the series resistors R ₁ and R ₂ and the ground terminal 34, and the output of the first output transistor Q ₄ of the current mirror circuit 31 is given to the base. A switching transistor Q ₆ , a resistor R 3 connected between the constant voltage terminal 33 and the base of the transistor Q ₂ , and a resistor R ₃ connected between the base of the transistor Q ₂ and the ground terminal 34
and a second _{output transistor of the current mirror circuit 31 connected between the interconnection point of the series resistors R 4 and R 5 and the} ground terminal 34. a switching transistor _Q7 whose base is given the output of _Q5 ; and an output terminal 3 connected to the base of the transistor _Q1 .
5, the collector of the transistor Q ₂ and the power supply terminal 36 connected to the current mirror circuit 31, the emitter common connection point of the differential pair transistors Q ₁ and Q ₂ , and ground. and a constant current source 36 connected between the terminal 34 and the constant current source 36 .

In the above one-terminal type triangular wave oscillation circuit, if the base potential V _A of transistor Q ₁ is lower than the base potential V _B of transistor Q ₂ , the transistor
Q ₁ is in an off state, transistor Q ₂ is in an on state, and current mirror circuit 31 and switching transistors Q ₆ and Q ₇ are each in an off state.
At this time, the base potential of transistor Q ₂ is at a high level, and its value V _{B (H)} is V _{B (H)} = V _r × R ₄ + R ₅ / R ₃ + R ₄ + R ₅ (1) There is.

In this state, the base potential V _A of the transistor Q ₁ is connected to the constant voltage source 3 by the capacitor C via the resistors R ₁ and R ₂ .
The base potential V A rises due to being charged from the transistor Q 2, and this base potential V _A becomes the base potential V _{B (H)} of the transistor Q ₂ .
When the size becomes equal to , the transistor Q ₁ is turned on, the current mirror circuit 31 is also turned on, and the switching transistors Q ₆ ,
Q ₇ also flips to the on state. As a result, the base potential of the transistor Q ₂ immediately becomes a low level, and its value V _{B (L)} is V _{B (L)} = V _r × R ₄ + R _Q7 /R ₃ + R ₄ + R _Q7 …(2 ) becomes. Here, R _Q7 is the on-resistance of the transistor Q ₇ and is generally much smaller than R ₃ , R _{4 , and R 5} , so V _B(H) > V _B(L) (3). Therefore, the above condition (transistor
A positive feedback effect works to keep transistor Q ₁ on and transistor Q ₂ off).

On the other hand, as mentioned above, the switching transistor
When Q ₆ is turned on, the base potential V _A of transistor Q ₁ begins to decrease as the charge of capacitor C is discharged via resistor R ₂ and on-resistance R _Q6 of transistor Q ₆ . When this base potential V _A becomes lower than the base potential V _{B (L)} , the transistor Q ₁ is inverted to the off state, and the current mirror circuit 31 and the switching transistors Q ₆ and Q ₇ are each inverted to the off state. The base potential of transistor Q ₂ becomes V _{B (H)} again, and transistor Q ₂
turns on, and the base potential V _A of transistor Q ₁ begins to rise again due to charging.

Oscillation is performed by repeating the above-described operations, and an oscillation output having a waveform as shown in FIG. 4 is obtained at the output terminal 35. Here, the oscillation amplitude
V _OSC is V _OSC =V _B(H) −V _B(L) =V _r {R ₄ +R ₅ /R ₃ +R ₄ +R ₅ −R ₄ +R _Q7 /R ₃ +R ₄ +R
_Q7 } =V _r (H-L) …(4) However, H=R ₄ +R ₅ /R ₃ +R ₄ +R ₅ …(5) L=R ₄ +R _Q7 /R ₃ +R ₄ +R _Q7 …(6) 1>H>L (7). Furthermore _, the oscillation period T is expressed as follows: _{T 1} is the charging mode period of the capacitor C, _and T ₂ is _the discharging mode _period . H-1)+-C(
R ₂ +R _Q7 )/ _lo (HL/H)...(8).

[Problems with background technology]

However, as mentioned above, the oscillation output obtained by charging and discharging using the CR time constant not only does not become an accurate triangular wave, but also the on-resistance R _Q6 of the switching transistor _Q6 is included in the discharge path, and the The low level V _{B (L)} of the base potential V _B , which is the reference voltage for the voltage comparison operation by the dynamic transistors Q ₁ and Q ₂ , is also affected by the on-resistance R _Q7 of the switching transistor Q ₇ . The above on-resistances R _Q6 and R _Q7 are the constant voltage source 32
, changes in the resistance value of each resistor R ₁ to _{R 5} , changes in the characteristics of transistors Q ₆ and Q ₇ , and the influence of these temperature characteristics, and as a result, the amplitude of the oscillation output V _OSC There is a drawback that the period T varies.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
The purpose of this is to obtain an accurate triangular oscillation waveform, to be able to accurately and easily set the oscillation amplitude and oscillation period, and to stabilize it, and to make the oscillation amplitude and oscillation period have the desired temperature characteristics. The object of the present invention is to provide a triangular wave oscillation circuit that enables this.

[Summary of the invention]

In order to achieve the above object, the triangular wave oscillation circuit of the present invention includes first and second transistors forming a differential pair, and a connection point between a common emitter connection point of the first and second transistors and a first power supply terminal. a constant current source connected between them, a third transistor whose collector and base are connected to the collector of the first transistor, and whose emitter is connected to the second power supply terminal; and a third transistor whose base is connected to the third transistor. a fourth transistor connected to the base of the transistor and whose emitter is connected to the second power supply terminal,
a first current mirror circuit whose input is the collector current of the first transistor; and a fifth current mirror circuit whose collector and base are connected to the collector of the second transistor and whose emitter is connected to the second power supply terminal. a sixth transistor, the base of which is connected to the base of the fifth transistor, the emitter of which is connected to the second power supply terminal, and the collector of which is connected to the base of the first transistor;
a second current mirror circuit consisting of a transistor whose input is the collector current of the second transistor; and a second current mirror circuit whose base and collector are connected to the fourth transistor.
a seventh transistor whose emitter is connected to the collector of the transistor and whose emitter is connected to the first power supply terminal; and whose base is connected to the base of the seventh transistor and whose collector is connected to the collector of the sixth transistor. an eighth transistor whose emitter is connected to the first power supply terminal, whose base is connected to the base of the seventh transistor, whose collector is connected to the base of the second transistor, and whose emitter is connected to the base of the second transistor; a third current mirror circuit comprising a ninth transistor connected to the first power supply terminal; a resistor having one end connected to the base of the second transistor; and a third current mirror circuit comprising a ninth transistor connected to the second transistor; and a capacitor connected to the base of the first transistor.

That is, the triangular wave oscillation circuit of the present invention connects a constant voltage source to the base of the second transistor forming a differential pair with the first transistor via a resistor, and determines whether or not a constant current is caused to flow through the resistor. Therefore, switching the potential of the base of the second transistor,
Further, a capacitor is connected to the base of the first transistor forming a differential pair with the second transistor, and this capacitor is charged and discharged with the same constant current as the constant current flowing through the resistor. .

By charging and discharging the capacitor with a constant current in this manner, an accurate triangular wave oscillation waveform can be obtained. Further, the oscillation amplitude is equal to the hysteresis voltage width determined by the constant current and the resistance value, and can be set accurately. Further, the oscillation period can be easily and accurately set only by the values of resistance and capacitance, and desired temperature characteristics can be provided.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a one-terminal type triangular wave oscillation circuit which is an integrated circuit, and 1 is a power supply terminal, 2 is a constant voltage terminal, 3 is a ground terminal, and 4 is an output terminal. _Q1 ,
Q ₂ is a differential amplification NPN transistor forming a differential pair, and a common emitter connection point thereof is connected to the ground terminal 3 via a constant current source 5 . The first current mirror circuit 6 has a PNP type input transistor Q ₃ and an output transistor Q ₄ .
The input transistor Q ₃ is connected between the power supply terminal 1 and the collector of the differential amplification transistor Q ₁ , and the emitter of the output transistor Q ₄ is connected to the power supply terminal 1 . The second current mirror circuit 7 has a PNP type input transistor Q ₅ and an output transistor Q ₆ , and the input transistor Q ₅ is connected between the power supply terminal 1 and the collector of the differential amplification transistor Q ₂ . The emitter of the output transistor Q ₆ is connected to the power supply terminal 1, and the collector is connected to the base of the differential amplification transistor Q ₁ to form a first negative feedback loop. There is. Third
The current mirror circuit 8 has an NPN type input transistor Q ₇ and two output transistors Q ₈ and Q ₉ , and the input transistor Q ₇ is the output transistor of the first current mirror circuit 6.
The output transistor Q ₈ is connected between the base of the differential amplification transistor Q ₁ and the ground terminal ₃ to provide a second negative feedback. The output transistor Q ₉ is connected between the base of the differential amplification transistor Q ₂ and the ground terminal 3 to form a positive feedback loop. A resistor R is connected between the base of the transistor Q ₂ for differential amplification and a constant voltage terminal 2, and a constant voltage is supplied to the constant voltage terminal 2 from a constant voltage source 9.
_Vr is applied. Further, the base of the differential amplification transistor _Q1 is connected to an output terminal 4, and this output terminal 4 is grounded via an oscillation capacitor C.

In the circuit with the above configuration, now the transistor
If the base potential V ₁ of Q ₁ is lower than the base potential V ₂ of transistor Q ₂ , transistor Q ₁ is in the off state, transistor Q ₂ is in the on state, and the second
The current mirror circuit 7 is the transistor Q ₂
is driven to the on state by the collector current of the first
The current mirror circuit 6 and the third current mirror circuit 8 are in an off state. Therefore, at this time, the transistor Q ₉ is in an off state, and the base potential V _{2 (H)} of the transistor Q ₂ at this time is approximately equal to the constant voltage V _r .

V _2(H) V _r …(9) In the above state, transistor Q ₆ is on,
Since transistor _Q8 is in the off state, the capacitance C
is charged by the output current I ₆ of the second current mirror circuit 7. Here, the output current _I6 is equal to the input current of the second current mirror circuit 7, and this input current is equal to the on-current of the transistor Q2, that is, the constant current Io of the constant current source 5, so the output current of the transistor Q1 is equal to the on-current of the transistor _Q2 , that is, the constant current Io of the constant current source ₅ . The base potential V ₁ increases linearly with time t, and when the increase in the base potential V ₁ is expressed as ΔV ₁ , the following equation holds true.

t・I ₆ =t・I ₀ =C・ΔV ₁ (10) And the base potential V ₁ is the base potential
When the current increases to the same level as V _{2 (H)} , the collector current of the transistor Q ₁ starts to flow, and as a result, the current starts to flow to the first current mirror circuit 6 and the third current mirror circuit 8, and the transistor Q ₉ starts to flow. The transistor Q ₂ is turned on, and a positive feedback operation is performed in which the base potential of the transistor Q 2 decreases to a low level V _{2 (L)} . At this time, since the current I ₉ of the transistor Q ₉ is equal to the current of the transistor Q ₁ , that is, the constant current I ₀ of the constant current source 5, the base potential of the transistor Q ₂
The change in V ₂ ΔV ₂ (hysteresis voltage width) is ΔV ₂ = V _{2 (H)} − V _{2 (L)} = V _r − (V _{r −} I ₉ × R) = I ₀ × R …(11) . At the same time, the transistor Q ₂ is turned off, the second current mirror circuit 7 is turned off, and the third current mirror circuit 8 is turned off.
Since the output transistor Q ₈ is in the on state and its current I ₈ is equal to the constant current I ₀ , the base potential V ₁ of the transistor Q ₁ decreases linearly with time t, and the decrease in the base potential V ₁ When expressed as −ΔV ₁ , the following equation holds true.

t・(−I ₈ )=t・(−I ₀ )=C×(−ΔV ₁ )…(12) Then, the base potential V ₁ is the base potential
When the voltage drops to the same level as V _2(L) , the transistor is turned off again.
Q ₁ is in the off state, the first current mirror circuit 6,
The third current mirror circuits 8 are each turned off, and a positive feedback operation is performed in which the base potential of the transistor Q ₂ becomes high level V _{2 (H)} again.
At this time, transistor _Q2 is in the on state,
The second current mirror circuit 7 is also turned on,
Capacitor C is charged again by current I ₆ (=I ₀ ).

Oscillation is performed by repeating the above-described operations, and an oscillation output having a waveform as shown in FIG. 2 is obtained at the output terminal 4. In this case, since the capacitance C is charged or discharged by the same constant current I ₀ ,
Accurate triangular waveforms can be obtained. Also, the amplitude V _OSC of the oscillation output is equal to the hysteresis voltage width, V _OSC = V _{2 (H)} − V _{2 (L)} = I ₀ × R (13), and the values of constant current I ₀ and resistance R It can be easily and accurately set. Here, when the constant current source 5 and the resistor R are integrated into an integrated circuit, generally I ₀ =
Since it is expressed as V _rr /R ₀ (V _rr is the reference voltage and R ₀ is the resistance), V _OSC = I ₀ × R = V _rr × R / R ₀ , and even if the value of the resistor R varies, the resistance Since the ratio R/R ₀ is constant, the oscillation amplitude V _OSC is stable. In this case, by selecting the temperature characteristics of the resistor R, the oscillation amplitude can be given a desired temperature characteristic. Moreover, the period T of the oscillation output is determined by the sum of the charging mode period T ₁ and the discharging mode period T ₂ of the capacitor C, T=T ₁ +T ₂ =C×V _OSC /I ₆ +C×V _OSC /I ₈ =2×C×V _OSC /I ₀ =2×C×R …(14) It can be easily and accurately set only by the values of capacitance C and resistance R, and it can be set easily and accurately by changing the constant current source current I ₀ and power supply voltage. It is stable regardless of etc. In this case, by selecting the temperature characteristics of the capacitance C and the resistance R, the temperature characteristics of the oscillation period T can be set.

〔Effect of the invention〕

As described above, the triangular wave oscillation circuit of the present invention can obtain an accurate triangular wave oscillation waveform, can accurately and easily set the oscillation amplitude and oscillation period, and can be stabilized, and also has the desired temperature characteristics for the oscillation amplitude and oscillation period. This makes it suitable for implementation as a one-terminal integrated circuit oscillator circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the triangular wave oscillation circuit of the present invention, FIG. 2 is a diagram showing operating waveforms of the circuit in FIG. 1, and FIG. 3 is a circuit diagram showing a conventional triangular wave oscillation circuit. FIG. 4 is a diagram showing operating waveforms of the circuit of FIG. 3. Q ₁ , Q ₂ ... Differential pair transistor, Q ₃ to _{Q 9} ...
Transistor, R...Resistance, C...Capacitance, 2...
Constant voltage terminal, 3...ground terminal, 4...output terminal,
5... constant current source, 6... first current mirror circuit, 7... second current mirror circuit, 8... third current mirror circuit, 9... constant voltage source.

Claims (1)

[Claims] 1. First and second transistors forming a differential pair
Q ₁ , Q ₂ , a constant current source connected between the emitter common connection point of the first and second transistors Q ₁ and Q ₂ and a first power supply terminal; transistor
A third transistor Q 3 is connected to the collector of Q ₁ and whose emitter is connected to the second power supply terminal _, and whose base is connected to the base of the third transistor Q ₃ and whose emitter is connected to the second power supply terminal. Consisting of a fourth transistor Q ₄ connected to the terminal,
a first current mirror circuit 6 whose collector current of the first transistor _Q1 is input; and a collector and base of which is connected to the second transistor;
It is connected to the collector of Q ₂ , and the emitter is connected to the 2nd collector above.
a fifth transistor Q ₅ connected to the power supply terminal of
The base is connected to the base of the fifth transistor _Q5 , the emitter is connected to the second power supply terminal, and the collector is connected to the first transistor Q5.
The sixth transistor Q ₆ connected to the base of Q ₁
a second current mirror circuit 7 which receives the collector current of the second transistor _Q2 as an input; and a second current mirror circuit 7 whose base and collector are connected to the fourth transistor Q2.
_Q4 is connected to the collector, and the emitter is connected to the first
a seventh transistor Q ₇ connected to the power supply terminal of
and an eighth transistor whose base is connected to the base of the seventh transistor _Q7 , whose collector is connected to the collector of the sixth transistor _Q6 , and whose emitter is connected to the first power supply terminal.
Q ₈ , and the base is the seventh transistor Q ₇
A third current mirror circuit 8 comprising a ninth transistor Q ₉ whose collector is connected to the base of the second transistor Q ₂ and whose emitter is connected to the first power supply terminal. , a resistor R whose one end is connected to the base of the second transistor _Q2 , a constant voltage source connected to the other end of the resistor R, and a capacitor connected to the base of the first transistor _Q1 . A triangular wave oscillation circuit characterized by comprising: C. 2. Claim 1, characterized in that the constant voltage source and the capacitor C are integrated circuits.
The triangular wave oscillator circuit described in section.