Junction Field-Effect Transistors

Abstract

The junction field-effect transistor (JFET) was first analyzed by Shockley in 1952 (Shockley, 1952). Because its conduction process involves predominately one kind of carrier, the JFET is called a unipolar transistor to distinguish it from the bipolar transistor. Based on Shockley’s theoretical treatment, the first working JFET was reported by Dacey and Ross (1953). The junction field-effect transistor has several key features. First, it has no surface effects, such as interface traps occurring at the oxide—semiconductor interface. As a result, the noise level associated with the current fluctuation due to capture and release of free carriers at the surface effects is very low. Second, the isolated two gate terminals of a JFET allow two different input signals to be applied simultaneously for signal-mixing purposes. Third, the carrier transport in a JFET is made up predominantly of the majority carriers, and thus the switching speed of a JFET is not limited by the minority carrier charge storage such as that in a bipolar junction transistor. The main drawbacks of JFETs are that the structure is not compact and the JFET is a low-current-handling device and is thus not suitable for power amplification.