How MOSFET works as a Linear Regulator

We already know above the MOSFET which is a type of field effect transistor. In this post, you’ll learn the operation of MOSFET as Linear regulator and its practical applications.

MOSFET as Linear Regulator

A MOSFET has three terminals:

  1. Gate
  2. Drain
  3. Source
Let’s consider that 4 volts are applied across Vgs now the current flows through the transistor from drain to source. The red curve in the graph below illustrates the change in current Id with a change in voltage across Vds. At 0 volt there is no current flowing through the circuit. When the voltage is sufficient the current increases linearly with the voltage up to a point where it saturates. 
mosfet-as-linear-regulator
In the linear region the current increases linearly with the voltage. But after reaching saturation the curve is not linear. We can say that in linear region MOSFET act as a resistor.
Now if the Vgs is changed we again obtain the same linearity (green curve) however the angle is now changed. This property of MOSFET in linear mode is used to obtain a linear regulator. Practically a MOSFET in linear mode can be used in low power applications. It is through a DC-DC converter with comparatively smaller efficiency.
The video below illustrates it is a clear way:

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