I found the following problem in the Rashid book of microelectronic circuits. I am looking to solve it but I don't even know where to start. How can I solve everything? What results do you get so I can compare?

The MOSFET amplifier of Fig. P5.33 has:

  • \$R_S=500\Omega\$
  • \$R_D=R_L=5k\Omega\$
  • \$R_{G_1}=7M\Omega\$
  • \$R_{G_2}=5M\Omega\$
  • \$K_p=20\frac{mA}{V^2}\$
  • \$V_t=3.5V\$
  • \$\left\lvert{}V_M\right\rvert=200V\$
  • \$V_{DD}=12V\$


  1. The input resistance \$R_{in}=\dfrac{v_s}{i_s}\$.
  2. The no-load voltage gain \$A_{v_O}=\dfrac{v_O}{v_g}\$.
  3. The output resistance \$R_O\$.
  4. The overall voltage gain \$A_v=\dfrac{v_L}{v_s}\$.



1 .first find out DC biasing values using voltage division to find \$ r_o= \frac{|V_A|} {I_D} \$ and \$g_m=\frac{2I_D}{V_{ov}}\$

2 . Draw this small signal equivalent circuit for MOSFET.


simulate this circuit – Schematic created using CircuitLab

3.Find the values of

  • \$A_{vo} =-g_m(r_o || R_D)\$
  • \$ R_{in} = R_G \$ where \$ R_G = R_{G1} || R_{G2}\$
  • output resistance \$ R_o=r_o || R_D\$
  • overall voltage gain \$ A_v=\frac{R_{i}}{R_{in}+R_{sig}}.A_{vo}\$

For any transistor amplifier, you can follow the steps below to analyze.

  1. Draw the ac equivalent of the circuit by replacing capacitors with a short circuit and nullifying independent DC sources.

  2. Replace the transistor with its equivalent model.

  3. Use KCL and KVL to calculate what you want.


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