Block diagram analysis of vacuum-tube circuits

MANY AUTHORS OF textbooks on electronics begin their discussion of feedback amplifiers with the now-classic block diagram, from which they derive the general gain equation,
$A^{\prime}={A \over 1-A \beta}\eqno{\hbox{(1)}}$
where A is the gain without feedback and β is the feedback fraction. In dealing with specific circuits, however, it is a common practice to write and solve the circuit equations. This article shows that amplifiers and oscillators can be analyzed from start to finish by block diagram methods, first developed for feedback control systems
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and later applied to purely circuit problems.
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