Bistable Multivibrator Working And Signal Waveform

Bistable Multivibrator Working 

Bistable multivibrator working
Bistable mul­ti­vi­bra­tor working 

Bistable mul­ti­vi­bra­tor working 

Bistable Mul­ti­vi­bra­tor Work­ing con­tains two sta­ble states. Both states are con­vert­ed only by apply­ing exter­nal trig­ger puls­es. It is also known as Flip Flop multivibrator. 

When the sup­ply is switched ON due to the slight mis­match between the two tran­sis­tors the con­duc­tion of one tran­sis­tor is more than other. 

We assume that the con­duc­tion of Q1 is more than Q2. Hence IC1 is greater than IC2 and VC1 is less than VC2. By the regen­er­a­tive feed­back actions the con­duc­tion of Q1 again increas­es and Q2 decreas­es. Final­ly Q1 goes to sat­u­ra­tion and Q2 goes to cut­off. Now the volt­ages of VC1 =Low, VC2 high, VB1 = less pos­i­tive and VB2 = ‑VBB

This state is a sta­ble state. It is con­vert­ed only by apply­ing pos­i­tive trig­ger pulse to the base of Q2 or a neg­a­tive trig­ger pulse to the base of Q1.

Bistable Mul­ti­vi­bra­tor sig­nal waveform

When a prop­er trig­ger pulse is applied the con­duc­tion of Q2 increas­es and the con­duc­tion of Q1 decreases. 

By the regen­er­a­tive feed­back actions Q1 goes to cut­off and Q2 goes to sat­u­ra­tion. Now the volt­ages of VC1 = high, VC2 = low, VB1 = ‑VBB and VB2 = less positive 

This state is also a sta­ble state. It is again con­vert­ed either by apply­ing a pos­i­tive pulse to the base of Q1 or a neg­a­tive pulse to the base of Q2. The capac­i­tors C1 and C2 are called speed up capac­i­tors used for increas­ing the speed of operation. 

Hence in bistable mul­ti­vi­bra­tors both states are con­vert­ed only by apply­ing prop­er exter­nal trig­ger pulses.

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