A-C temperature compensation and integrated amplifiers

One of the more troublesome characteristics of a transistor is its rather pronounced sensitivity to temperature.1,2 Consequently, in the design of a transistor circuit it is necessary to provide diligently for changes in device parameters resulting from both self-heating effects and ambient variations. Of primary importance is the stabilization of the d-c operating point.3,4 In addition, it is often necessary to obtain temperature-stable a-c performance in a transistor circuit. In the case of small signal amplifiers, an analytical basis for a-c temperature compensation is not generally available at the present time.5 This paper describes a fairly simple yet accurate design theory whereby the temperature variations in the transistor small signal parameters are effectively compensated by a minimum of passive elements. The result is an integrated amplifier whose current gain, voltage gain, power gain, input impedance, and output impedance are virtually insensitive to temperature. The amplifier is termed integrated since the required compensation may best be accomplished first, by analyzing the circuit as an entity, and second, by mounting all components on or within a common substrate.