Low-frequency operation of four-terminal field-effect transistors

Interesting and useful behavior is obtained by operating a two-gate field-effect transistor as a four-terminal device. This paper considers important aspects of the low-frequency four-terminal behavior of a transistor with symmetrical geometry. The functional dependence of the drain current upon gate bias voltages and material and structural constants is determined, and four general modes of operation of the device are defined. For each mode the dependence of relevant transconductances on gate biases is calculated. Special cases of interest are analyzed, including that in which the transconductance exhibits a linear variation with gate bias voltage. Experimental results are in good agreement with the theory.