UJT or Unijunction transistor
The UJT or Unijunction transistor is constituted by two polluted regions, with three external terminals: two bases and one emitter.
What is a Zener diode?
The Zener diode is a special type of diode that allows the flow of current on the opposite direction of the arrow of the diode. This diode does not conduct until the applied voltage reaches or is greater of the breakdown voltage. Zener diode is very popular as Voltage reference element.