JPH0227632Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to improvements in monostable multivibrator circuits.

BACKGROUND OF THE INVENTION A monostable multivibrator circuit is triggered to produce a pulsed output when an input signal exceeding a predetermined reference voltage is applied.

Figure 1 is a circuit diagram using an operational amplifier showing an example of a conventionally commonly used monostable multivibrator circuit.
and a resistor 2, and only the positive side of this differential output is taken out by a diode 3 and supplied to the non-inverting input terminal of an operational amplifier 4. Further, a resistor 5 is connected between this non-inverting input terminal and the ground, and a timing capacitor 6 is further provided between this non-inverting input terminal and the output terminal.

On the other hand, the inverting input terminal of the operational amplifier 4 is configured so that the output of a reference voltage generation circuit composed of resistors 7 and 8 and a capacitor 9 is supplied as a reference voltage Vr. When a signal exceeding 100 Ω is applied to the non-inverting input of operational amplifier 4, a single pulse signal with a width determined by the value of capacitor 6 is output.

In this case, in order to prevent fluctuations in the reference voltage Vr and to simplify the circuit, it is better to apply a positive trigger to the non-inverting input terminal of the operational amplifier 4. In this case, the trigger voltage needs to be higher than the reference voltage Vr. It is.

However, in the monostable multivibrator circuit with the above configuration, since only the timing capacitor 6 is connected between the non-inverting input terminal of the operational amplifier 4 and its output terminal, the instantaneous The impedance is short-circuited to the output side of the operational amplifier 4 and becomes extremely small. That is, when the resistance value R ₁ of the resistor 5 and the output impedance r ₀ of the operational amplifier 4 are compared, R ₁ >>r ₀ is satisfied. Therefore, the instantaneous impedance at the non-inverting input terminal
Since the timing capacitor ₆ is momentarily in a shorted state, Z 0 becomes extremely small as Z ₀ =r ₀ . As a result, it becomes difficult to apply a trigger, so the time constant of the differentiating circuit must be increased, and if the time constant is increased, a narrow pulse output cannot be obtained, which poses a problem.

DISCLOSURE OF THE INVENTION Accordingly, it is an object of the present invention to provide a monostable multivibrator circuit using an operational amplifier that is easy to trigger and easily provides a narrow pulse output.

To achieve this purpose, the present invention reduces the instantaneous impedance of the non-inverting input by connecting a resistor in series with the timing capacitor provided between the non-inverting input and the output of the operational amplifier. The structure is such that a narrow pulse output can be obtained by preventing a decrease in the pulse width and making it easier to apply a trigger.

In a circuit configured in this way, a drop in instantaneous impedance at the non-inverting input terminal to which one end of the timing capacitor of the operational amplifier is connected is prevented, and the time constant of the differentiating circuit is accordingly increased. This has an excellent effect in that a narrow pulse output can be easily obtained because there is no need to do this.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 2 is a circuit diagram showing one embodiment of a monostable multivibrator circuit according to the present invention.
The same parts as in the figures are indicated using the same symbols. In the figure, 10 is a resistor connected in series with the timing capacitor 6 connected between the non-inverting input terminal and the output terminal of the operational amplifier 4. That is, the difference between FIG. 2 and FIG. 1 is that this resistor 10 is provided.

Here, if the value of the resistor 10 is R ₂ , then the resistor R ₁
and R ₂ and the output impedance of operational amplifier 4 r ₀
The relationship is as follows.

R ₁ > R ₂ ≫ r ₀ ...(1) Therefore, the instantaneous impedance Z ₀ at the non-inverting input terminal of the operational amplifier 4 is due to the resistor 10 being connected in series with the timing capacitor 6. As a result, Z ₀ = R ₂ + r ₀ ≒ ...(2). As a result, the instantaneous impedance increases significantly compared to the case shown in Figure 1, and as a result, a drop in the level of the trigger input is prevented, making it easier to trigger and even with a thin differential pulse. It will be easily triggered.

Therefore, in the circuit with the above configuration, since a drop in instantaneous impedance at the non-inverting input terminal of the operational amplifier is prevented, it becomes easier to apply a trigger, and it is also possible to easily trigger even a thin differential pulse. Therefore, it has various excellent effects such as being able to easily obtain a narrow pulse output.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a monostable multivibrator circuit, and FIG. 2 is a circuit diagram showing an embodiment of the monostable multivibrator circuit according to the present invention. 1... Capacitor, 2, 6, 9... Capacitor,
2, 5, 7, 8, 10...resistance, 3...diode,
4...Operation amplifier.

Claims (1)

[Scope of utility model registration request] In a monostable multivibrator circuit that is triggered by supplying a reference voltage to the inverting input terminal of an operational amplifier and supplying a positive input signal to the non-inverting input terminal with a timing capacitor connected between it and the output terminal. , a monostable multivibrator that prevents a drop in instantaneous impedance at the non-inverting input terminal by connecting a resistor in series with the timing capacitor, making it easier to trigger and providing a narrow pulse output. circuit.