Transient power dissipation in a transistor switch with capacitive load

The transient power dissipation in a transistor switch with capacitive load and base-current drive is analysed in terms of the charge-control parameters of the transistor. It is shown that the effect of shunt load capacitance is to increase the peak and average power dissipation during the turn-on period and to decrease the dissipation during the turn-off period. Expressions are developed for the peak and average collector power dissipation during the turn-on and turn-off periods of the transistor. Since the expressions are not amenable to direct solution, numerical methods are used and the results are presented in graphical form. Experimental and theoretical results are compared and found to be within reasonable agreement.