JPS5816267Y2 - pulse oscillation circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a pulse oscillation circuit suitable for IC implementation.

FIG. 1 shows an example of a conventional pulse oscillation circuit of this type, and first, the operation of this circuit will be explained.

Now, when the power supply +Vcc is turned on and the charging/discharging capacitor Co for creating the sawtooth wave is not charged at all as shown in 11, the second transistor TR2, one of the differential pairs, is off, so the fifth transistor Transistor T Hs tri is off, therefore, the first and fourth transistors TRI #
Both TR4 are also off, so the base potential of the other third transistor TR3 of the differential pair is the resistance R5=
The value VB is determined by the partial pressure ratio of R6*R7.

From this state, charging of the charging/discharging capacitor C8 is started via the variable resistor R8 for adjusting the oscillation frequency, and as a result, the potential at point A rises as shown in Figure 2 A and exceeds the above-mentioned value vH at t2. , the second transistor TR2 is turned on, and thereby the fifth transistor TR5 is turned on, so that the first transistor TR2 is turned on. The fourth transistors TR1sTR4 are both turned on.

Therefore, from t2, the discharge of the charging/discharging capacitor C8 begins with the resistor R1.
and the first transistor TR1, and at the same time the base potential of the third transistor TR3 is connected to the resistor R5*.
The partial pressure ratio of R6 is almost determined, and the value vL is lower than the above ■H.
become.

From this state, as the capacitor C6 discharges, the potential at point A gradually decreases as shown in Figure 2 A, and when it drops below the above-mentioned value VL at t3, the second transistor TR2 turns off, and the third transistor TR3 turns on and returns to the initial state.

Therefore, the rectangular wave pulses shown in FIG. 2 are obtained at the 8 collector points of the sixth transistor TR6, which is turned on and off in response to the fifth transistor TR5.

By the way, in the circuit shown in Fig. 1, the oscillation frequency, that is, the repetition frequency of the output rectangular wave pulse r (Fig. 2) is adjusted by adjusting the charging slope of the charging/discharging capacitor C8 as indicated by the broken line in Fig. 2 A using the variable resistor RQ. It is now done by changing it like this.

Therefore, when the charging/discharging capacitor C6 is discharging, the potential at point A changes by the change in the variable resistor R8, and thereby the discharge slope also changes as shown by the broken line.

This means that the pulse width of the output rectangular wave pulse changes from Tw to Tw' in FIG. 2 as the oscillation frequency changes.

Therefore, the present invention takes these points into consideration and proposes a pulse oscillation circuit suitable for IC implementation that can always obtain a rectangular wave pulse with a constant pulse width even when the oscillation frequency is changed.

FIG. 3 shows an embodiment of the pulse oscillation circuit of the present invention, and this circuit will be explained below.

Now, as in the case of Fig. 1, when the power supply +Vcc is turned on, t1
Assuming that the charging/discharging capacitor Co is not charged, in this state, one of the second transistors TR2 of the differential pair
is off and the other third transistor TR3 is on, so the fifth transistor TR5 is on, and therefore the 1m4th sixth transistor TR1-TR4-
Both TR6 are turned on.

Therefore, the potential of the third transistor TR3 is equal to the emitter potential of the fourth transistor TR,i and the resistor R6e R7.
The button is turned off when the value V□ determined by the voltage division ratio of is reached, and charging of the charging/discharging capacitor C8 is started via the first transistor TR1 and the resistor R1.

From this state, charging of the charging/discharging capacitor C8 progresses, and A
The potential at the point rises as shown in Fig. 4A, and at t2 it reaches the above-mentioned value v.
When the voltage exceeds H, the second transistor T R2 turns on.
, since the third transistor TR3 is turned off, the fifth transistor TRs is also turned off, and thereby the first, fourth, and sixth transistors TR1-TR4*TR6 are all turned off.

Therefore, from t2, the charging/discharging capacitor C8 starts discharging via the resistor R1 and the variable resistor R8 for adjusting the oscillation frequency.
At the same time, the base potential of the third transistor TR3 is determined by the voltage dividing ratio of the diode D1 and the resistor R5*R6*R7.
The above-mentioned vH and υ also become low values VL.

From this state, the discharge of the charge/discharge capacitor Co progresses, and A
The potential at the point decreases as shown in Fig. 4A, and at t3 it reaches the above-mentioned value v.
When the voltage drops below L, the second transistor TR2 is turned off and the third transistor TR3 is turned on, returning to the initial state.

Therefore, the rectangular wave pulse shown in FIG. 4 is obtained at these 228 points of the sixth transistor TR6.

The diode D1 is for temperature compensation of the VBE of the fourth transistor TR4.

In the circuit shown in FIG. 3, the oscillation frequency is adjusted by changing the discharge slope of the charging/discharging capacitor CO as indicated by the broken line in FIG. 4 using the variable resistor R8.

Therefore, considering the photovoltaic time of this capacitor Co, C
The potential at the point is given by c5 - vBE1, where c5 is the collector potential when the fifth transistor TR5 is in the off state and VBEI is the base-emitter voltage of the first transistor TR, regardless of the adjustment of variable resistor R8. constant.

This means that the charging slope of the charging/discharging capacitor C8 does not change even if the variable resistor R8 is adjusted, and therefore,
As the frequency of the output rectangular wave pulse changes as shown by the broken line at the beginning of Figure 4, the pulse width becomes constant 'rw.

As detailed above, the pulse oscillation circuit of the present invention can always extract a rectangular wave pulse with a constant pulse width even when the oscillation frequency is changed, and has a configuration suitable for IC implementation, making it effective. It is something.

[Brief explanation of the drawing]

Figures 1 and 2 are circuit diagrams of conventional pulse oscillation circuits and □
It is a waveform chart explaining operation. 3 and 4 are a circuit diagram and a waveform diagram for explaining the operation of one embodiment of the pulse oscillation circuit of the present invention. co...charging/discharging capacitor, Ro...variable resistor for adjusting oscillation frequency, TR1 to TR5...
First to fifth transistors.

Claims (1)

[Scope of utility model registration request] A charging/discharging capacitor for creating a sawtooth wave is connected between the power supply and the grounding point via a first transistor and a resistor.
A variable resistor for adjusting the oscillation frequency is connected between the connection point of the transistor and the above-mentioned resistor and the contact point, and the voltage generated in the charge/discharge capacitor is applied to the pace of one of the second transistors of the differential pair. , the base of the other third transistor of the differential pair is connected to the voltage dividing midpoint of the voltage dividing resistor connected between the power source and the ground point, and one of the voltage dividing resistors on the power source side is bridged. A fifth transistor is provided in which the fourth transistor and the first transistor are connected so as to be conductive when the third transistor is turned on. A pulse oscillation circuit that can always extract square wave pulses with a constant pulse width from 5 transistors.