Applications of a Transistor

Applications of a Transistor – BJT,UJT & FET

Applications of a Transistor

Applications of a Transistor

Transistor is an electronic device made of three layers of semiconductor material that can act as an insulator and a conductor. Let’s see the various applications of a transistor – BJT,UJT & FET.

Applications of a Transistor – Bipolar Junction Transistors

The transistor is a three-layer semiconductor device consisting of either two n- and one p type

  • Transistor as a switch: When used as an electronic switch, the transistor is normally operated alternately in cut-off and saturation regions.
  • Transistor as amplifier: Due to the small changes in base current the collector current will mimic the input with greater amplitude.

Applications of a Transistor – UJT

A Unijunction Transistor (UJT) as the name implies, is characterized by a single pn junction.

  • Phase control.
  • Relaxation oscillator.
  • Timing circuits.
  • Switching
  • Pulse generation.
  • Sine wave generator.
  • Voltage or current regulator supplies

Applications of a Transistor – Field Effect Transistor

Field effect Transistor is a semiconductor device which depends for its operation on the control of current by an electric field.

Phase shift oscillators:

The high input impedance of FET is especially valuable in phase shift oscillator to minimize the loading effect.

In voltmeters:

The high input impedance of FET is useful in voltmeters to act as an input stage.

Other use of a Transistor:

  • As a buffer amplifier which isolates the preceding stage from the following stage.
  • FET has low noise operation. So, it is used in RF amplifiers in FM tuners and communication equipment.
  • FET has low input capacitance, so it is used in cascade amplifiers in measuring and test equipment.
  • Since FET is a voltage-controlled device, it is used as a voltage variable resistor in operational amplifiers and tone controls.
  • FET has low inner modulation distortion. So, it is used in mixer circuits in FM and TV receivers, and communication equipment.
  • Since it is low-frequency drifts, it is used in oscillator circuits.

Applications of a Transistor – MOSFETs

MOSFET is an important semiconductor device and is widely used in many circuit application.

  • Because of higher input resistance ,the enhancement type MOS devices have been used as micro-resistor in integrated micro-circuits.
  • For electrometer circuits where exceptionally low currents are to be measured MOSFETs are most nearly ideal.
  • MOSFET s are very small in size . which make them suitable for highly complex digital arrays.
  • MOSFET is used for switching and also amplifying electronics signals in the electronic devices.
  • It is used as an inverter.
  • It can be used in digital circuit.
  • MOSFET can be used as a high frequency amplifier.
  • It can be used as a passive element e.g. resistor, capacitor and inductor.
  • It can be used in brushless DC motor drive.
  • It can be used in electronic DC relay.
  • It is used in switch mode power supply (SMPS).


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