Some factors in the design of wide-band amplifiers for television

The figure of merit of a wide-band amplifier is the ¿stage-gain times bandwidth¿ for a stated attenuation at the edges of the band. However, it is necessary also that the phase error within the band should not be too great, that the cost of components should not be excessive, that the circuit should be easy to set up and that the response should not vary unduly with changes in the valve characteristics. Some of the earliest wide-band amplifiers consisted of stagger-tuned circuits based on the Butterworth filter. The properties of orthodox filters were utilized in ¿dead-end¿ coupling networks and ¿chain¿ amplifiers, the stage-gain times bandwidth of the chain amplifiers being theoretically unlimited. Modern theory has defined upper limits to the stage-gain times bandwidth for various types of coupling networks. The practical design of a wide-band amplifier for a television transmitter or receiver involves making the best compromise between the theoretical upper limit for the figure of merit and the other conditions mentioned above.