For the small signal circuit below, use Thevenin analysis to determine an expression for the input resistance (R). Note that "g" represents the gain for the current source.

Hand Calculation: Since you now have the values of R1 and R2 resistors, obtain numeric value of voltage gain Av=Vo/Vi, and numerical values of input and output resistances Ri and Ro. Note that you need to DC analysis first. Do a hand calculation and calculate the DC collector current or IC. This is needed in order to calculate the small signal parameters gm and rπ and in turn to obtain the Av , Ri and Ro Hence, first perform a DC analysis (use the circuit in Figure 1 and take all capacitors open) and assume your transistor has a β=140.

An operational amplifier consisting of three cascaded stages has a voltage gain of 3500. The gain of the first two stages is known to be -5 and -900. What is the voltage gain of the last stage and which type of MOSFET amplifier would you prefer for this stage?

Figure 6 shows a circuit where feedback is provided between the drain and gate of the transistor M1 Q6 Draw the small signal equivalent circuit of the open loop circuit obtained by breaking the loop at the gate of transistor M1 (suitable for the analysis in the mid band frequency range). Consider Cg as short circuit in the model and state any assumption. (a) (b) State the necessary conditions for the oscillation to occur in the circuit. Using the conditions from (b), derive an expression for the amplifier oscillation frequency fo. (c) Derive the necessary condition for the oscillation to occur in the circuit and state if you can conclude that the circuit will oscillate when considering the values of the inductances L2 = 8 LI = 2 mH; capacitors C = 2 nF; transconductance of the transistor gml = 1.4 mS; and resistors R1 = R2 = Rs : 10 k2. (d) %3D L2 L, R, Cg. C Vout Cp M1 R2 CG Rs Cs Vss = 0 V Figure 6

4) Below is the small signal model of a multistage amplifier. Using this model, write the equationsthat you would need to determine the voltagegain. IMPORTANT: You only need to providethe equations that you would need to determinethe voltage gain. You DO NOT need to combine and simplify the equationsto determine a final expression for the voltagegain. Vin Vo Vb vo1 Rb R13 Vbe1 Vbe2 'e gm 1 Vbe1 gm 2 Vbe2 Rc2 Rc1 Re