Question

Problem 3 +12 V MOSFET Parameters 0-0, are matched devices 200 2 = 2.0mA/V/2 λ=0 x0.2 (body effect) 0.8 V GI 12 V S1 75 Ω 2, 02 -12 V This problem is designed to illustrate the principle of impedance matching and the relationships between the DC bias current of a MOSFET and its ac circuit parameters. We would like to choose a DC value of drain current, Iog, so that Rm matches the generator's resistance Rs. In other words, how do we make Rm 75 Ω? Let's take it step-by-step. A. The amplifier's configuration is common- B. Sketch a small-signal model for the amplifier. Carefully label component values and signal voltages and currents. Identify Ra and v, on your sketch. [The following questions demonstrate how the DC and ac circuit parameters are interdependent. C. From your model, derive an expression for Rn of the amplifier as a function of g and the device parameters D. We would like to design the amplifier so that its input resistance, R matches the 75 Ω source. What value of gn is required? E. Ifv- 1 mV, and with Rn matched to 75 2, find the ac value of v, in mV. F. For the value of gn needed in part D, what quiescent DC drain current, Ino, is required? IThe following questions are concerned with the circuit's behavior at DC.J G. What value of leer is needed to produce the value of Ino required in part F? H. For the value of leer determined in question G, solve the circuit for Qi's DC terminal voltages Vo, Vs, Vpi, and Vosi And finally, the remaining questions are concerned with I. Using your model from question B and the value of v, determined in question E, solve for the si the circuit's ac behavior/ (ac) voltage at the output, vo J. The voltage gain (/v) of this circuit is relatively low. How could you increase it?

Answer 1