Mosfet Drain current Equations

Knowing how to solve the MOSFET equation is an important thing in circuit design, as MOSFETs are used in most applications as a Switch. To mention the working of MOSFET in simple terms, we will control the flow of drain current by applying a voltage between the Gate and Source terminals.

The calculation of drain current depends on which region the MOSFET is working in.

Regions of MOSFET:

There are three regions of operation for MOSFETs.

  1. Cut off region
  2. Linear or Ohmic or triode region
  3. Saturation region
If the Gate-Source voltage(Vgs) is less than the gate threshold voltage(Vth), mosfet will not turn on, and we call it as Cut off region.

If the Gate-Source voltage(Vgs) is more than the gate threshold voltage(Vth), and mosfet turns on, it can work either in the Linear or in the saturation region, depending on the applied Drain to Source Voltage(Vds). I have written the equation in the solution solver tool for solving the circuit.




By using the above equations, we can solve the MOSFET circuits. I have been solving quite a few circuits. Let's discuss them in future articles.

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