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).

Connecting base and collector turns BJT into diode.

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

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]


  1. ^ http://www.ti.com/lit/an/sboa058/sboa058.pdf [bare URL PDF]
  2. ^ "Usage of a transistor configured as diode".
  3. ^ "Electronic Device and Circuit Theory Electronics: Common Circuit Application(JFET Diode)". 17 March 2009.