JPH0238509Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a monostable multivibrator that is triggered by the falling edge of a pulse.

Conventionally, monostable multivibrators have been made using two transistors as shown in Figure 5, or using an amplifier as shown in Figure 6, but both require a large number of parts and are expensive. It had drawbacks.

The present invention is intended to improve this, and the present invention will be explained below with reference to an embodiment shown in FIG. A series circuit is provided in which the cathode side of the diode D2 is connected to the anode side of the diode D1, the anode side of the diode D2 is connected to the base side of the transistor Q1, and the resistor R3 is connected to the collector side.

In the above circuit, if the connection point between resistor R1 and capacitor C1 is input, it is normally at a high potential as shown in Figure 2, and capacitor C1 is connected to resistor R1, capacitor C1, and diode D1 from power supply +B as shown by the solid line. The transistor Q1 is also in a conductive state. However, as shown in the figure, when the input voltage becomes low potential, the electric charge stored in the capacitor C1 is transferred to the resistor R2, the diode D2,
It discharges through the capacitor C1 as shown by the dotted line, and the base side of the transistor Q1 changes from +VF to -VCC+VF.
becomes negative, and the transistor Q1 is cut off. However, capacitor C1 and resistor R2
The charge in the capacitor C1 is discharged with a time constant of , and at the same time the base side of the transistor Q1 returns to the original +VF, the transistor Q1 becomes conductive again.

As explained above, the capacitor C1 and the resistor R1 serve as the charging time constant of the capacitor C1, and the resistor R2 and the capacitor C1 also serve as the discharging time constant. As shown in FIG. 2, when the fall of the input pulse is used as a trigger, the collector potential of the transistor Q1 can obtain a pulse potential with a predetermined width, and can be used as a monostable multivibrator. In this way, since a monostable multivibrator can be configured using one transistor Q1, the circuit configuration can be simplified and costs can be reduced.

Note that the transistor Q1 can be configured as either a PNP type or an NPN type. Furthermore, the resistor R1, capacitor C1, and diodes D1 and D in the circuit shown in FIG.
2 as a reference, a circuit including a resistor R4, a capacitor C2, and diodes D3 and D4 can be arranged in parallel as shown in FIG. 3, and transistors Q3 and Q2 can be provided on the input side, respectively. The timing chart of such a circuit is as shown in FIG.
Using this as a trigger at the falling edge of the transistor Q3 side and the falling edge of the transistor Q2 side, a pulse voltage of a predetermined width can be obtained respectively. These output signals can be used, for example, as a mute circuit when switching signals.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram of a monostable multivibrator showing an embodiment of the present invention, Fig. 2 is a timing chart of voltages at various parts of the circuit, and Fig. 3 is a circuit diagram to which the monostable multivibrator of the present invention is applied. 4 is a timing chart of the transistor voltage of the circuit of FIG. 3, and FIGS. 5 and 6 are connection diagrams of a conventional monostable multivibrator, respectively. In the figure, Q1, Q2, Q3 are transistors, R
1, R2, R3, R4 are resistors, D1, D2, D
3. D4 is a diode, C1, C2 are capacitors.

Claims (1)

[Scope of utility model registration request] A series circuit of a resistor R1, a capacitor C1, and a diode D1 connected to a DC power supply, and a series circuit of a resistor R2 and a diode D2 are provided.
2 is connected in series in the forward direction to the diode D1,
The connection point between the resistor R2 and the diode D2 is connected to the base side of the transistor Q1, and the resistor R1
A monostable multivibrator characterized in that the input is a connection point between the transistor Q1 and the capacitor C1, and the output is output from the collector of the transistor Q1.