Transient Response of Multistage Video-Frequency Amplifiers

The response to a Heaviside unit voltage is set forth as the most logical and relevant criterion of the fidelity of video-frequency amplifiers. The part of the transient response that is governed by the high-frequency amplitude and phase-delay characteristics of amplifiers may be approximated closely by the steady-state response to a square wave having a suitable period and thus may be expressed in a Fourier series. Simplicity and rapidity of numerical calculation are the outstanding advantages of the steady-state formulation. As an illustrative example of the method the transient response of several multistage compensated resistance-coupled amplifiers are computed. Considerable data helpful in the design of amplifiers of this type are presented. It is concluded: (1) The wave-shape distortion of a Heaviside unit voltage is accumulative as the number of stages is increased. (2) The value of the damping constant K= RVL/ C should lie between 1.51 and 1.61. (3) The resonant frequency fo = 1/( 2r, rVLC) determines the slope of the wavefront of the transient response. R is load resistance; C is the total shunt capacitance; and L is the compensating inductance in series with R. It is proposed that the oscillographic response of video-frequency amplifiers and the associated transmission apparatus to a square wave be considered as a part of performance tests of future television systems.