TABLE OF CONTENTS This article describes the available gain amplifier design which is derived from the transducer gain equation. This method can be used to design amplifiers for any gain up to the maximally stable gain for unconditionally stable and potentially unstable devices.
By Les Besser and Rex Frobenius
From APPLIED MICROWAVE & WIRELESS, VOL. 8, NO. 2, SPRING 1996
A previous article discussed how to design amplifiers for the maximum achievable gain, G Tmax, of an unconditionally stable two-port device, using the transducer gain technique [1, 2], The method provided a unique set of source/load impedances that simultaneously conjugately match the device. Since maximum-gain two-port devices provide excellent input/output match, these amplifiers are readily cascadable and are highly popular among system designers. Although the transducer gain design method works well in many cases, it has some shortcomings:
In low-noise and linear power amplifiers, the source and load terminations must be determined by other considerations that require special design techniques.
If the system requirements specify gains less that the maximum gain, an infinite number of source/load combinations could provide the desired gain. In such cases, the transducer gain technique leads to tedious iterative manipulations.
The transducer gain approach is not convenient for potentially unstable devices for which the input-output interaction may be so significant that finding a suitable and stable source and load pair may prove impractical.
This article discusses a special amplifier design technique called the available gain [1] design, derived from the transducer gain equation. The available...
