Find the small-signal gain expression of the following circuits. Express the answer in small-signal parameters. Assuming all transistors are in the saturation region. All voltages labeled with upper-case are just DC voltages, which should not be involved in the gain expression.
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Find the small-signal gain expression of the following circuits. Express the answer in small-signal parameters. Assuming all transistors are in the saturation region. All voltages labeled with upper-case are just DC voltages, which should not be involved in the gain expression.
![For the circuit shown in Fig. 4 below, all BJT transistors are in the forward-active region and MOS transistors are in the saturation region. VB1 and VB2 are two DC voltages. Include small-signal output resistance ro into the answers if necessary. Numeric answers are not necessary. (a) Find small-signal output resistance Ro (i.e. looking into output node vo) of the amplifier. [10 points] (b) Find the voltage gain vo/vin of the amplifier [Hint: (vo/vx)⋅(vx/vin), where vx is signal voltage at the base terminal of Q2]. [16 points] (c) If DC voltage VB2 is increased while M4 is still in the saturation region, what is the impact on the voltage gain magnitude |vo/vin| of the amplifier? Provide explanations to your answer. [5 points] Fig. 4](https://www.doubtrix.com/uploads/editor/5131112827vPcHWBtGDE.png)
