Pulse and Digital Circuits

8.4 COMMUTATING CONDENSERS

In the initial stable state Q₂ is ON and in saturation, Q₁ is OFF. Once a trigger is applied [see Fig. 8.3] to change the state of the devices in the monostable multivibrator, because of the stray capacitances of the devices they may not go into the next state immediately. This is a problem which needs to be overcome.

Now, let a negative pulse be applied at the base Q₂ to drive it into the OFF state and consequently Q₁ into the ON state. Prior to the application of this trigger the voltage at the second collector was V_CE(sat). On the application of a trigger at t = 0, as Q₂ goes into the OFF state, the voltage at its collector rises from V_CE(sat) to V_CC. Let the change in voltage at the second collect be v_i, a step ...