1 ECE2280 Homework #4 Spring 2008 1. a) Draw the cross section of a mosfet. b) Explain in your own words and drawings as needed how, when(under what conditions), and in what direction the current flows in the mosfet. c) Explain in your own words all the different regions for Fig. 4.6 by drawing cross-sections of the mosfet to correspond to each region in that figure and explaining how each region operates(i.e. how the channel looks, how the current flows, etc). Fig 4.6 Fig. 4.11 2. a) Explain in your own words the difference between Fig. 4.6 and Fig. 4.11 . b) What equation and region of operation is graphed in Fig. 4.12. Fig 4.12 c) Explain in your own words how the PMOS differs from the NMOS transistor. 3. Analyze the circuit at the right to determine the voltages (VD, VG, VS) at all nodes and the currents through all branches (5 currents). Let Vt=2V and kn’(W/L)=2A/V2. Neglect the channel length modulation effect (i.e. λ=0). +10V 2V DV DI SI 20Ω SV 10Ω + +10V 1kΩ 1kΩ GV GI2 4. Solve the circuit to the right to find VS. Assume λ=0 and |Vt|=1, kn’(W/L)=1mA/V2. 5. Use: Vt=1V, Kn’(W/L)=10µA/V2 , λ=0 VI = 5+0.001sin(10t) Assume all capacitors are open for DC analysis and shorted for AC analysis (a) Solve for the DC currents: IG, ID, and IS (b) Solve for the DC voltages: VG, VS,and VD (c) State the operating point, bias point, or quiescent point for this amplifier 6. Use the circuit from at the right(solved in 5 for DC). (a) Draw the small-signal equivalent circuit (e) Analyze the small-signal circuit for VS/VI. 7. Use: Vt=2V, Kn’(W/L)=100µA/V2, λ=0 VI = 3+0.001sin(10t) Assume all capacitors are open for DC analysis and shorted for AC analysis (c) Solve for the DC currents: IG, ID, and IS (d) Solve for the DC voltages: VG, VS,and VD (c) State the operating point, bias point, or quiescent point for this amplifier 8. Use the circuit at the right. (Solved in 7 above for DC). (a) Draw the small-signal equivalent circuit (e) Analyze the small-signal circuit for VD/VI. 1kΩ SV +10V 2V DV DI 20Ω SV 10Ω 100mF 10kΩ GV GI + ~ SV 100mF SI 20V 8V 5V ++10V -5V +10V 3V GV DV DI SI GI0= 10mF 1kΩ 1kΩ 10Ω SV ~