Question

Q5. Consider the circuit in Fig.1 (right). Assume 9m, 9o, VT, W, L, Mn, and Cox of the transistor are knwon and isolation capacitors are sufficiently large. Assume the transistor operates in saturation. (1) Find input resistance Rin (5 marks). (2) Find output resistance Rout (5 marks). (3) Find voltage gain v./vs (10 marks).

Answer 1

Solution! The io a This is a common common so source Amplifier. Cr مقام waalit Circuit- RG Caupled common source of Here C. > Blocking capacitor - 4 - Coupling capacitor. C and q provides DC isolation to Bices So, that external elements do not disturb the DC operating point. le Vos , Ios) G - Source By pass capacitor is connected to prevent the decrease i'm voltage gain, Draw medium frequency AC equivalent Circuit. Where (Ren = Rp 11R₂ ) Reacras) IR)

To draw medium frequency Ae equivalent CRT, Replace r Large Capacitor = short circuit small Capacitor a open Circuit Source Ground Now, Replace the MOSFET with small signal modelia - Invas . Here Re = RD Figure ①] Ric Ru ② Input Risoo Resistance ! no Resistance ! Resrstance Biasin (in mag where, I Ri's R E Ner input Resistance by I'mcluding the efreet of Biasing Resistor, le (Rina Ral where. Ru= (R, 11R2) i (Rina Re 1122 ] ourput Resistance Disable Vs. Digable R (ie Ro) Apply Use accross Cuepur port. Q7 b) C)

Im Wash Srds and Uro (Due to Short circuit) So, dependent Source - No use, since, Us=o. Gare is shorted to source 4. Vazo Vas=o... No use of Ra and Hence, Imuasa (ox vas) ( vas =o) Current Roards Ron Vasl Ro o voltage gain! Auteur) = (MODES Au = (Im Nas Ri) from Figure 6 (Au = - Jom Re] where ^= (ras !! RO) ve Sign indicates the phase Shift of lao,