Last modified on 21 July 2009, at 19:14

Semiconductor Electronics/Field Effect Transistor/Introduction

FET or Field effect transistors are device that find applications just as BJT does but vary on how they operate. BJT is a current controlled device, that is the current that flows via the collector terminal is a function of base current I_c = f(I_b) \,. Whereas in FET, the current flowing in it is controlled by the voltage.

FET is similar to BJT. It has a source which is analogous to emitter BJT. It has a drain which is analogous to collector in BJT and has a gate which is similar to base in BJT. The current in FET flows from source to drain, and is a function of voltage applied between gate and source I_{FET}=f(V_{GS}) \,.

FET's normally have very high input impedance that ranges from few ohms to mega ohms. It has simpler construction and is easy to put in Integrated Circuits. FET's have more temperature stability than BJT. There are different type's of FET's as follows

  • JFET (Junction Field Effect Transistor)
  • MOSFET (Metal Oxide Semiconductor Field Effect Transistor)