Study of transfer characteristics and output characteristics of Metal Oxide Semiconductor Field Effect Transistor (MOSFET)

Objective:

Design and construct a suitable circuit and determine the transfer characteristics and drain characteristics of an N- channel enhancement-mode MOSFET. 

Theory:  

A MOSFET is a voltage controlled device and requires a only a small input current. The switching speed of MOSFET is very high and the switching time s are of the order of nanoseconds It Has very high input impedance and works at very high switching frequency. MOSFETs are of two types namely Enhancement type and Depletion type. Each type are subdivided into two types namely p-channel and n-channel. IRF 540 is an n-channel enhancement MOSFET. An n-channel enhancement MOSFET has N substrate with p-impurities on other side. A thin layer of metal oxide is deposited over the left side of the channel. A metallic gate is deposited over the silicon di-oxide layer which is an insulator. Hence gate is insulated from the channel and for this reason MOSFET is sometimes called insulated gate FET.

Apparatus  / Components  Required:

Circuit Diagram:

Procedure: 

  • Transfer Characteristics
  1. Check the components / Equipment for their working condition.
  2. Connections are made as shown in the circuit diagram.
  3. Set VDS to some convenient voltage.
  4. Increase VGS gradually and note down the corresponding changes in drain current ID.
  5. Repeat the above step for different value of VDS.
  6. A graph of VGS Vs ID is plotted and from the graph Trans conductance is calculated.
  • Output Characteristics
  1. Set VGS to some convenient voltage greater than threshold voltage VT.
  2. Increase VDS gradually and note down the corresponding changes in drain current ID.
  3. Repeat the above step for different value of VGS.
  4. A graph of VDS Vs ID is plotted and from the graph drain resistance is calculated.

 

Result & Analysis:

Trans conductance    gm = ∆ID / ∆VGS = __mho

Drain Resistance     RD = ∆VDS / ∆ID = ___Ω

Conclusion:

Should follow result in conformation with theory.

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