Microwave properties and applications of negative conductance transferred electron devices

Abstract

The transferred electron effect in epitaxial GaAs has been used to realize a semiconductor device which exhibits a stable negative conductance over a wide range of microwave frequencies and power levels. These devices have been used in conjunction with circulator coupled networks to design high-level wide-band transferred electron amplifiers which have a voltage gain bandwidth product in excess of 10 GHz for frequencies from 4.0 to about 16.0 GHz. Linear gains of 6-12 dB per stage and saturated output power levels in excess of ½ W have been realized. The physical and electrical properties of these devices are described with regard to the achievement of a stable negative conductance. The influence of several parameters (i.e., device temperature, bias voltage, circuit loading, etc.) is discussed with regard to device and circuit stability. Measurements of the terminal admittance of several typical devices as a function of the bias, input power, and frequency have been used to study their microwave properties. The large signal data are used to compute the relationship between the available device power and the magnitude of the negative conductance independent of the test circuit. This same measurement technique can provide a simulation of the performance of any nonlinear negative conductance, without the need for circuit design and load tuning. In addition, an analytical large signal model of the negative conductance has been used to predict the large signal performance of the active device (i.e., gain compression, conversion efficiency, etc.) in both oscillator and amplifier circuits.