Static and dynamic performance of micropower transistor logic circuits

Digital transistor circuits operating in the "micropower" range (viz., 1 to 1000 µw per gate) are needed in the portable electronic equipments of a modern field army. The most basic micropower transistor requirements are, 1) junction reverse currents which are small compared with minimum operating currents, 2) useable device current gains at minimum operating currents, and 3) minimum junction capacitances in order to enhance switching speed. The micropower performance capabilities of modified direct coupled transistor logic (DCTL), diode transistor logic (DTL) and transistor transistor logic (TTL) circuits are sufficient to satisfy the present and projected requirements of many portable equipment applications. The normal operating temperature range, logic capability, and tolerance immunity of the circuits need not be compromised. Somewhat reduced stability margins may be necessary but are permissible due to lower operating power levels. Markedly reduced operating speeds are unavoidable but not at all detrimental since audio clock frequencies suffice for many portable equipments. In order to maintain adequate over-all performance, a minimum saturated transistor collector current ICSis required in a micropower logic gate. This minimum is most sensitive to the maximum operating temperature of the circuit. The feasibility of implementing a particular micropower circuit design by means of hybrid thin-film techniques or integrated silicon techniques depends principally on the large total circuit resistance values encountered in micropower designs.