Diode-connected transistor

A diode-connected transistor is a method of creating a two-terminal rectifying device (a diode) out of a three-terminal transistor. A characteristic of diode-connected transistors is that they are always in the saturation region for metal-oxide-semiconductor field-effect transistors (MOSFETs) and junction-gate field-effect transistors (JFETs), and in the active region for bipolar junction transistors (BJTs).

A diode-connected transistor is made by connecting

  • the base and collector of a BJT
  • the drain and source of a JFET[1]
  • the gate and drain of a MOSFET
Connecting base and collector turns BJT into diode.

Diode-connected transistors are used in current mirrors to provide a voltage drop that tracks that of the other transistor as temperature changes.[2] They also have very low reverse leakage currents.[3]

References
  1. http://www.ti.com/lit/an/sboa058/sboa058.pdf
  2. http://electronics.stackexchange.com/questions/50633/transistor-configured-as-diode
  3. http://electronicscircuit1.blogspot.com/2009/03/common-circuit-applicationjfet-diode.html
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