TABLE OF CONTENTS This article describes the operating gain method for amplifier design. Derived from the transducer gain equation, this method is recommended for linear power amplifiers.
By Les Besser and Rex Forbenius
From APPLIED MICROWAVE & WIRELESS, VOL. 8, NO. 4, NOVEMBER/DECEMBER 1996
In previous articles [1, 2], we discussed amplified design for the maximum gain, G MAX, of an unconditionally stable device, using the transducer gain technique, and for low-noise amplifiers with the available gain procedure. The former method provided a unique set of source/load impedances which simultaneously provide a conjugate match for the device, while the latter approach allowed consideration of trade-offs between gain and noise performance by choosing a desirable source impedance and a match for the output port of the device. The available gain technique is a special case of the transducer gain definition, which can be used to design an amplifier with a gain less than the maximum G MAX or maximum stable gain (MSG) [1], regardless of the stability condition of the active device.
In this article, we cover a third amplifier design technique called the operating gain [3] method, also derived from the transducer gain equation. The operating gain method selects the load impedance first, then matches the resultant input impedance, a technique recommended for linear-power amplifiers, where the load is the more important of the two terminations.
The transducer power gain is given by (see Figure 1):
where
represents the input reflection coefficients of the two-port device with arbitrary load...
