The Steady-State and Transient Analysis of a Feedback Video Amplifier

A two-stage feedback video amplifier is analyzed on the transient and steady-state bases, and a simplified design procedure is developed for each approach. Using the transient response of the amplifier to a step-voltage input as a basis, design curves have been prepared which allow determination of the necessary amplifier parameters when either the rise time (10 to 90 per cent of final amplitude) and the per cent transient overshoot, or alternatively, the per cent transient overshoot and the net gain, are specified. The effect of changes in-transconductance and resistor values on the output wave form is discussed. The low-frequency distortion of the input wave as a result of the interstage-coupling network is also considered, and a relation for the increase in the effective interstage time constant is derived. The steady-state response of the amplifier is examined in considerable detail, particular emphasis being given to provide an analysis which integrates with the transient study. It is found that an amplifier can be uniquely detemined by means of design curves, provided the overshoot in the steady-state characteristic and the frequency for 3-db attenuation, or alternatively, the midband gain and the overshoot in the steady-state characteristic, are known. In addition, the improvement in steady-state low-frequency response is determined.