JPS6234414A - Triangular wave oscillation circuit - Google Patents

Abstract

PURPOSE:To obtain a triangular wave oscillation circuit which generates an accurate triangular wave oscillation waveform and whose oscillation amplitude and oscillation period are set accurately and easily by combining a differential pair of transistors (TR) and a current mirror circuit. CONSTITUTION:The potentials of the bases of the differential pair of TRs Q1 and Q2 are switched according to whether a current is flowed through a resistance R between one base and a constant voltage terminal 2, and a capacitor C between the other base and a ground terminal is charged and discharged with the same current. Thus, the capacitor is charged and discharged with the constant current to obtain the accurate triangular oscillation waveform and the oscillation amplitude becomes equal to hysteresis voltage width determined by the constant current and the value of the resistance and is set accurately. Further, the oscillation period is set easily and accurately only by the values of the resistance and capacitor and desired temperature characteristics are obtained.

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 as, for example, a one-terminal type integrated circuit oscillation circuit.

[Technical background of the invention]

FIG. 3 shows a conventional integrated circuit (IC) L terminal triangular wave oscillation circuit, in which a differential pair transistor QleQ! for differential amplification voltage comparison is shown. and the above transistor Q
An input transistor Q driven by a collector current of s
3 and 1st. Second output transistor Q4 - Qs
A current Haller circuit 31 having: a constant voltage terminal 33 to which a constant voltage vr is applied from an external constant voltage source 32; and the transistor Q! nine series resistors R1+R1 connected between the base of the current mirror circuit 3Z, and the first output transistor Q4 of the current mirror circuit 3Z connected between the interconnection point of the series resistors R, , R, and the ground terminal 34. a switching transistor Q6 whose output is given to its base; a resistor R3 connected between the constant voltage terminal 33 and the base of the transistor Q3; and a resistor R3 connected between the base of the transistor Qs and the ground terminal 34. Series resistance R
4, R, and a switching transistor Q7 which is connected between the interconnection point of the series resistor R4+RS and the ground terminal 34, and whose base is supplied with the output of the second output transistor Qs of the current mirror circuit 31; The transistor Q! An oscillation capacitor C externally connected to an output terminal 35 connected to the base of the transistor Q, a power supply terminal 36 connected to the collector of the transistor Q and the current mirror circuit 31, and an emitter of the differential pair transistors Q1+Q2 , and a constant current source 36 connected between the common connection point and the ground terminal 34.

In the one-terminal type triangular wave oscillation circuit described above, when the base potential ■ of the transistor Q1 is lower than the base potential v1 of the transistor Q1, the transistor Ql is in an off state;
Transistor Ql is in an on state, and current mirror circuit 31 and switching transistors Q6+Q7 are each in an off state. At this time, transistor Q! The base potential of is at a high level, and its value VB(H) is.

In this state, the base potential vA of the transistor Q1 rises as the capacitor C is charged by the constant voltage source 32 via the resistor R1+R1, and this base potential vA rises to the R-segment potential V of the transistor Qz. , (H), the transistor Q1 is turned on, the current Haller circuit 31 is also turned on, and the switching transistor Qs = Qy is also turned on.

By this, transistor Q! The base potential of Vm immediately becomes a low level, and its value Vm (t,) becomes. Here, R, A is the on-resistance of the transistor Q7, and is generally very small compared to Rs + R4 * Rg K, so Vl(if) > Vll(L) −
(3) becomes. Therefore, the above state (transistor Q
1 is on and transistor Q1 is off).

On the other hand, when the switching transistor Q6 is turned on as described above, the base potential vA of the transistor Qs
is the resistance R and the on-resistance R1- of the transistor Q6
Since the charge in the capacitor C is discharged through the capacitor C, it starts to decrease.

When this base potential V becomes equal to or lower than the base potential Vl (L), the transistor Ql is inverted to the off state, and the current mirror circuit 31 and the switching transistor Qs
, Qγ are each inverted to the off state, so that the transistor Q! The base potential of the transistor Q3 becomes the Vm(g) again and the transistor Q3 is turned on, and the base potential vA of the transistor Q1 starts 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 @vo,c is vOIC""1(H) -vl(L)=Vr(H-L
)...(4)1)H)L
...(7). Also, the oscillation period T is the period of the charging mode of the capacitor C! , the period of discharge mode is expressed as T, 'r='rt+'r.

It is.

[Problems with background technology]

However, the oscillation output obtained by charging and discharging using the CR time constant as described above not only does not become an accurate triangular wave, but also has the on-resistance RQ6 of the switching transistor Q6 in the discharge path, and the differential transistor Qt t Q
*Base potential V serving as the reference voltage for voltage comparison operation using K
The low level VB (L) of B is also smooth, and the length transistor Q
It is affected by the on-resistance RQ of 7. Above on-resistance RQ
81Rq7 is the potential change of the constant voltage source 32, each resistor R1~
It is impossible to avoid the effects of changes in the resistance value of R, changes in the characteristics of the transistors Qa and Qr, and their temperature characteristics, and there is a drawback that the amplitude Mo1e and period T of the oscillation output fluctuate accordingly.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose 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 the oscillation. An object of the present invention is to provide a triangular wave oscillation circuit that allows amplitude and oscillation period to have desired temperature characteristics.

[Summary of the invention]

That is, in the triangular wave oscillation circuit of the present invention, a resistor is connected between one base of a differential pair transistor and a constant voltage terminal, and the potential of the base is cut off depending on whether a constant current is caused to flow through this resistor or not. In other words, a capacitor is connected between the other base of the differential pair transistors and the ground terminal, and this capacitor is charged and discharged with the same constant current.

By charging and discharging the capacitor with a constant current in this manner, an accurate triangular wave oscillation waveform can be obtained.

Furthermore, the oscillation amplitude can be accurately set to be equal to the hysteresis voltage width determined by the constant current and the resistance value. Further, the oscillation period can be easily and accurately set only by the values of resistance and capacitance, and it is possible to provide desired temperature characteristics.

[Embodiments of the invention]

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

Figure 1 shows a one-terminal triangular wave oscillator circuit integrated into an integrated circuit. are NPN type transistors for differential amplification forming a differential pair.
The ivy common connection point is connected to the ground terminal 3 via a constant current source 5. The first current Haller circuit 6 has a PNP type input transistor Ql and an output transistor Q4, and the input transistor Q3 is connected between the power supply terminal 1 and the collector of the differential amplification transistor Q1. The terminal of the output transistor Q4 is connected to the power supply terminal IK. The second current circuit 7 has a PNP type input transistor Qs and an output transistor Q, and the input transistor Ql is connected between the power supply terminal l and the collector of the differential amplification transistor Qs. ), its output transistor Q
No. 6 is connected to power supply terminal 1, and its collector,
is connected to the base of the differential amplification transistor Q1 to form a first negative feedback loop. The third current mirror circuit 8 includes NPN type input transistors Q1.
It has two output transistors Qs+Q9, the input transistor Q7 of which is connected between the collector of the output transistor Q4 of the first current transistor 6 and the ground terminal 3; The output transistor Q8 connects the base of the differential amplification transistor Q1 and the ground terminal 3.
The output transistor Q is connected between the differential amplification transistor Q! to form a second negative feedback loop. and the ground terminal 3 to form a positive feedback loop. A resistor R is connected between the base of the differential amplification transistor Q2 and a constant voltage terminal 2, and a constant voltage vr is applied to this constant voltage terminal 2 from a constant voltage source 9. . 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 IC.

In the circuit configured as described above, if the base potential v1 of the transistor Q1 is now lower than the base potential 2 of the transistor Q1, the transistor Q1 is in the off state, the transistor Qz is in the on state, and the second current Haller circuit 7 is driven to the Zion state by the collector current of the transistor Q2, and the first current slurry circuit 6 and the third
The circuit 8 is in the off state. Therefore, the transistor Q9 is in an off state at this time, and the transistor Q! The base potential Vz (11) is approximately equal to a constant voltage ■1 ~ 1°Vg (H) vr...(9) In the above state, transistor Q6 is off, transistor Q
Since @ is in the on state, the capacitor C is charged by the output current I of the second current mirror circuit 7. Here, the output current 6 is equal to the input current of the second current mirror circuit 7, and since this input current is equal to the on-current of the transistor Q2 and the constant current IO of the constant current source 5, the base of the transistor Ql The potential v1 increases linearly with time t, and when the increase in the base potential v1 is expressed as ΔVl, the following equation holds true.

t-l5=t-l6=C-ΔV, , -.alpha.Q, and the base potential v1 is the base potential V! (11
), the collector current of the transistor Q1 starts to flow, and as a result, the first current starts to flow to the error circuit 6, the third current mirror circuit 8,
Transistor Q- turns on, and transistor Q!
A positive feedback operation is performed in which the base potential of Vz(b)K decreases to a low level Vz(b)K. At this time, the transistor Q
Since the current I9 of 9 is equal to the current of the transistor Q1 and the constant current of the constant current source 5, the base potential of the transistor Qz is V! Change in ΔV! (Hysteresis voltage width) is ΔV! = Vz (a) −Vg (L)=v, −
(vr-I, xR): I, X R...α■. At the same time) Rannosta Q! is off,
The second current slurry circuit 7 is in the off state, whereas the output transistor Q8 of the third current slurry circuit 8 is in the on state, and the current generator 8 is connected to the constant current I,
Therefore, the base potential vl of the transistor Q1 decreases linearly with time t, and when the decrease in the base potential v1 is expressed as -Δ■1, the following equation holds true.

t・(-x,)=t-(-technical・)=cx (-ΔVt)
-t# Then, when the base potential v1 falls to the same level as the base potential 'h(L), the transistor Q1 is turned off again, and the first current slurry circuit 6 and the third current slurry circuit 8 are respectively turned off. Nashi, Transistor Q! The base potential of is again at high level Vz(II
), a positive feedback operation is performed. At this time, the transistor Q2 is turned on, the second current mirror circuit 7 is also turned on, and the capacitor fkC is again changed to the current Is("Io
) will be charged.

By repeating the above-described operations, oscillation is performed, and an oscillation output having a waveform as shown in FIG. 2 is obtained at the output terminal 4. In this case, Yong'! Constant current IoK with the same tC
Since the battery is charged or discharged frequently, an accurate triangular waveform can be obtained. Also, the amplitude V of the oscillation output. a is equal to the hysteresis voltage width, volC” Vz(a) −Vl(L)=IoXR・
...(to) It is possible to easily and accurately set the values of the gate, constant current construction@, and resistance R. Here, constant current source 5 and resistor B
When it is integrated into an integrated circuit, it is generally expressed as follows, and even if the value of resistance R varies, the resistance ratio
Since o is constant, the oscillation amplitude V. , C are stable.

In this case, by selecting the temperature characteristics of the resistor, the oscillation amplitude can be given a desired temperature characteristic. Moreover, the period T of the oscillation output is the charging mode period Tl of the capacity itC.
and discharge mode period T2, 'r:='rl +'rI =2xcxR=-64', and can be easily and accurately set using only the values of capacitance C and resistance R. It is stable regardless of constant current power supply construction, medium power supply voltage, etc. In this case, by selecting the temperature characteristics of the capacitor C1 and the resistor 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. ),
It is suitable for implementation as an l-terminal type integrated circuit oscillator circuit.

[Brief Description of the Drawings] 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 of Fig. 1, and Fig. 3 is a diagram showing a conventional triangular wave oscillation circuit. A circuit diagram showing the circuit, FIG. 4 is a diagram showing operating waveforms of the circuit of FIG. 3. Ql, Q! ...Differential pair transistors sQs~Q9...
・Transistor, R...Resistance, C...Capacitance, 2...
・Constant voltage terminal, 3...ground terminal, 4...output terminal,
5... Constant current source, 6... 1st current mirror circuit, 7... 2nd current mirror circuit, 8... 3rd current mirror circuit, 9... Constant voltage source. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (2)

[Claims] (1) Transistors Q_1 and Q_2 forming a differential pair, a constant current source connected to the common emitter connection point of the differential pair transistors Q_1 and Q_2, and the transistor Q_1
a first current mirror circuit 6 whose input is the collector current of the transistor Q_2; a second current mirror circuit 7 whose input is the collector current of the transistor Q_2 and whose output is connected to the base of the transistor Q_1; The output current of the current mirror circuit 6 becomes the input, and the first
the output of is connected to the base of the transistor Q_1,
A third current mirror circuit 8 whose second output is connected to the base of the transistor Q_2, a resistor R whose one end is connected to the base of the transistor Q_2, and a constant resistor R whose other end is connected to the base of the transistor Q_2. A triangular wave oscillation circuit comprising a voltage source and a capacitor C connected between the base of the transistor Q_1 and a ground terminal. (2) The triangular wave oscillation circuit according to claim 1, wherein the circuit other than the constant voltage source and the capacitor C is formed into an integrated circuit.