Some New Transistor Bistable Elements for Heavy Duty Operation

Bistable elements of fast switching speed (0.2
\mu
sec), capable of delivering load currents up to 100
ma
and having a low-output impedance, are required in many electronic circuits. Such an element is particularly useful in digital computers employing passive routing. The paper shows that circuits which use both
p-n-p
and
n-p-n
transistors are well suited for such duties. It also describes both nonsaturated and saturated forms. Part I devotes itself to nonsaturated circuits, and the analysis is mathematical in approach. The general properties thus deduced are applicable to all members of the circuit family. Part II turns to the problems introduced by saturation and is a general theoretical discussion of wide application. It leads to a concept denoted controlled saturation; this is applied to switching circuits in order to minimize the penalty of lost speed which saturation can cause. Part III applies the theoretical work of the preceding parts to a fast trigger circuit in which saturation is permitted. It concludes by showing that this basic saturated circuit can be developed into a variety of forms.