TRANSISTORS IN DIRECT CURRENT AMPLIFIERS
W. Guggenbühl · OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 1961
After a brief survey on the different methods of d-c amplification the problem of zero stability is treated in detail. The amplifiers are divided tnto two main groups, direct coupled types and chopper types. An equivalent circuit for d-c-drift in the active region of a transistor is shown, starting from the temperature dependence of characteristic d-c parameters. Remarks on aging are included. Some temperature compensated input stages with reduced drift are discussed. Different d-c amplifiers are compared using the equivalent drift power as a general measure for the performance of the circuits. An optimum source resistance for minimum drift power may be evaluated. The second part deals with chopper amplifiers. Transistor switching characteristics are compared with those of an ideal switch. Temperature variations of these characteristics and some circuit aspects of transistor choppers are discussed. In the last part the zero stability obtainable with these circuit techniques ts tabulated for some typical input stages. (auth)