Question

Draw the circuit for monostable multi if Q1 is ON and Q2 is OFF.

Answer 1

Fig.8p.2 The given circuit of the monostable multivibrator. Solution: (sat). (sat). 10 0.2 9.8 V. 1.96 kΩ. 5 mA ... Fig.8p.3 Circuit of the monostable. In the stable state: assume Q is OFF and Q is ON and in saturation ...

Answer 2

In the above circuit diagram we can find two transistors which are wired as switches. Please read the article Transistor as a Switch to know more about it. When a transistor is ON, it works in saturation region and its collector – emitter acts as a short circuit. When a transistor is OFF, it works in cut off region and its collector – emitter acts as an open circuit. So in the above circuit, when a transistor is in OFF state, its collector will have voltage equal to supply voltage Vcc and when the a transistor is in ON state, its collector will be grounded.

Function of resistor R is to limit collector current of both transistors Q1 and Q1. Resistors R1 & R2 will provide base current for transistors Q2 & Q1 respectively during ON condition. Capacitor C3 and Resistor R3 is designed as a differentiator circuit to provide sharp trigger pulses to the base of the transistor Q1. The diode D allows only positive pulses to the base. Capacitor C2 is optional, which is called as Speed Up capacitor. It is used for speedy bypassing of signal transitions (LOW to HIGH and HIGH to LOW) at the collector of Q2 to the base of Q1.


When the circuit is switched ON, transistor Q1 will be OFF and Q2 will be ON, which is its stable state. Transistor Q2 is ON since the base of the transistor is connected to Vcc via R1. Transistor Q1 will be OFF because base of the transistor is at 0v since transistor Q2 is ON.