Given the circuit, assume that the transconductance curve of FETs Q1 and Q2 follows the equation: ID = IDSS(1 − VGS/4)2 where IDSS = 4×10−3 A. Answer the following questions: (a) Determine the drain current ID and drain-to-source voltage VDS for FET Q1 and Q2. (b) Determine the source resistance rs of FET Q1. (c) Consider the resistance r0 looking into the drain of FET Q2. Ideally, this resistance approaches infinity, but for this FET, it is given as 10 MΩ. Calculate the voltage gain Av = Vout Vs of the amplifier. (Rs1 = Rs2 = 2 KΩ )
![[MOSFET Circuits] Consider the MOSFET circuit as shown below. R = 1kΩ, kn’ = 1 mA/V2 and Vtn = 0.3 V for both Q1 and Q2, W/L = 0.5μm/0.1μm for Q1, W/L = 1μm/0.1μm for Q2, λ = 0 and vSB = 0. (a) Calculate the voltage at the drain terminal of Q1. (b) What is the ratio of iD1 to iD2, where iD1 is the drain current for Q1 and iD2 is the drain current for Q2. Hint: This circuit is called the "current mirror" circuit, where the ratio of iD1 to iD2 is a fixed number, determined by W1, W2, L1 and L2, as long as both transistors are biased in saturation mode. (c) What is the maximum value of R2 so that Q2 remains in saturation mode?](https://www.doubtrix.com/uploads/editor/0609833589NADbRdqxAb.png)
![(a) Assume that the MOSFET in Figure 3.1 is operating in saturation and is characterised by a threshold voltage, VT = 1 V. Assume that the parameter, K = 1 mA/V2 where the drain-source current in the MOSFET in saturation is given by the usual expression: iDS = K2(vGS−VT)2 Calculate the output voltage, vo, for the circuit shown in Figure 3.1 when vIN = 2.5 V, Vs = 10 V, and R = 1 kΩ. The correct solution should satisfy both conditions necessary for the device to operate in saturation. Figure 2.1 [10 marks] (b) For the circuit in Figure 2.1, calculate the small signal voltage gain of the circuit, Av, at the operating point defined by the numerical values of part (a). Assume the input and output voltages include small signal components, vin and vout respectively. VIN and Vout correspond to the constant DC components of the input and output voltage from part (a). vIN = VIN +vin vOUT = VOUT +vout Av = vout vin [10 marks] (c) Determine the small signal output impedance at the terminals labelled a and b for the circuit shown in Figure 3.1 and at the operating point defined by the numerical values of part (a). [10 marks]](https://www.doubtrix.com/uploads/editor/3475428305cJOidAHSIp.jpg)
