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I am trying to solve a problem on using an FET transistor as an amplifier with the common source configuration. The model should be appropriate for high frequencies.

The problem gives the equivalent circuit for the AC analysis like below where gm is 4 mA/V:

Equivalent circuit

To model the circuit I used the DC circuit of the amplifier with common source and ended up with this:

Equivalent DC circuit

I found that Rg = Ri and Rs is given. But I am having difficulty in finding Rd and proper Vcc and Vss sources to make it work. Any advice on how to approach this problem would be appreciated.

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  • \$\begingroup\$ You need to bias the gate \$\endgroup\$
    – DKNguyen
    Commented Feb 3, 2020 at 16:12
  • \$\begingroup\$ Clarification: are you supposed to be using a MOSFET ot a JFET? \$\endgroup\$
    – brhans
    Commented Feb 3, 2020 at 16:16
  • \$\begingroup\$ @DKNguyen Isn't the scheme of polarizing the transistor with Vcc and Vss correct? \$\endgroup\$
    – David Prifti
    Commented Feb 3, 2020 at 16:17
  • \$\begingroup\$ @brhans any FET transistor is correct. I just happened to choose a MOSFET. \$\endgroup\$
    – David Prifti
    Commented Feb 3, 2020 at 16:17
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    \$\begingroup\$ You're using the MOSFET as NMOS, but the symbol indicates a PMOS transistor. The PMOS will be off as long as your gate voltage is above VSS. \$\endgroup\$
    – Cristobol Polychronopolis
    Commented Feb 3, 2020 at 16:35

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