1 ECE2280 Homework #5 Spring 2009 Use the circuit below for problems 1,2, and 3. Use Vt=2V, kn’(W/L)=3mA/V2, λ=0, Vs is an AC voltage source. 1. Find the DC values for currents and voltages at the gate, drain, and source. 2. Use the small-signal equivalent model to find the value for the gain Av=soVV, Rin(ignore the 2Meg as a source resistance), and Rout (ignore the 10k as a load resistor) by assuming all capacitors become shorts. 3. How could the overall gain be increased. By making that change, what is the tradeoff or what do you have to be careful about? Use the following amplifier for problems 4 and 5: Fig. 4.49 Let Rsig=100Ω, RD=10kΩ, RG=200kΩ, RL=10kΩ, Cgs=10pF, Cgd=1pF, CC1= CC2= CS=1µF, gm=2mA/V. 5K2K10k2Meg2Meg+ - Vo Rin Rout Vs Csig2 NMOS1kDC = 9VDC = 8V1020DC = 9V1k 4. Find the complete transfer function for the above circuit that includes the capacitors (i.e. treat all caps as an impendence). 5. Create the magnitude Bode Plot for the transfer function. Label the low 3dB. Use the following circuit for problems 6, 7, and 8: Let Vt=2V, kn’(W/L)=180µA/V2, ID=IS=10mA, and λ=0. 6. Draw the small-signal equivalent circuit by assuming all capacitors become shorts. 7. Analyze the circuit to find Av=Vo/Vin, Rin(remove 10Ω) and Rout 8. Explain how to change Rin to a more ideal value (greater than or equal to 1Meg). Explain how to increase the overall gain, Av. State the condition that needs to be satisfied for the ac input amplitude, Vin so that the circuit operates correctly. (what is the small-signal condition? Assume that the transistor is saturated) ID IS 10µF10Vin 1µFVo Rout 9V Rin 1Meg