Transistor current-switching circuits

The paper gives the analysis and d.c. design criteria with experimental results for high-speed current-switching circuits. Some improved forms of the basic current-switching circuits have been suggested. These modified circuits considerably ease the stringent tolerance requirements of the components and the power supplies of the original circuits in addition to reducing the number of components and power supplies used in the basic building block of the circuit. D.c. circuit analysis is presented for the modified single-transistor-type and also for the modified complementary-transistor-type circuits. Design equations and the pyramiding factors for various types of circuits have been discussed. Transient processes in current-switching circuits are considered in detail. It is shown that the major factors limiting the minimum delay per stage obtained is the emitter-base transition capacitance in addition to the risetime and hence the inherent frequency response of the transistors. A halfadder circuit and a wave-form generating circuit using current-switching mode is described.