Practice Assignment 5 - Microelectronic Circuits | ECE 3040, Assignments of Electrical and Electronics Engineering

Download Practice Assignment 5 - Microelectronic Circuits | ECE 3040 and more Assignments Electrical and Electronics Engineering in PDF only on Docsity! ECE3040 — Assignment 5 1. The figure shows the ac signal circuit for a combination common-source and common-drain amplifier. (a) Replace the MOSFET with its pi model. Assume that r0 =∞. Show that vos vtg = gmRts 1 + gmRts vod vtg = −gmRtd 1 + gmRts Note that one gain is positive and the other is negative. If Rts = Rtd, the gains are equal but of opposite signs. In this case, the circuit is called a “phase inverter.” (b) Replace the MOSFET with its T model. Assume r0 =∞. Show that vos vtg = Rtd rs +Rts vod vtg = −Rts rs +Rts (c) Show that the answers are equivalent. 2. A common-drain amplifier followed by a common-source amplifier is shown. (a) Replace the MOSFETs with the pi models and show that vo vtg1 = gm1 (r01kRts1) 1 + gm1 (r01kRts1) × gm2 × [− (r02kRtd2)] (b) Replace the MOSFETs with the T models and show that vo vtg1 = r01kRts1 rs1 + r01kRts1 × 1 rs2 × [− (r02kRtd2)] 1 (c) Show that the two answers are equivalent. 3. The figure shows a common-drain amplifier followed by a common-gate amplifier. The small- signal models of the n-channel and the p-channel devices are identical. (a) Assume that r0 = ∞. Replace the MOSFETs with the pi models and show that gm1vgs1 = −gm2vgs2, vtg1 = vgs1 + gm1vgs1RS − vgs2, and vo = −gm2vgs2Rtd2. Solve these equations to obtain vo vtg1 = gm1 1 + gm1RS + gm1/gm2 ×Rtd2 (b) Assume that r0 =∞. Replace the MOSFETs with the T models and show by inspection that vo vtg1 = 1 rs1 +RS + rs2 ×Rtd2 (c) Show that the answers are identical and explain which model makes this problem the simplest to solve. 4. The figure shows a common-source amplifier. It is given that V + = +20V, V − = −20V, K = 0.0015A/V, VTH = 1.75V, r0 = 40kΩ, RI = 200Ω, R1 = 1MΩ, R2 = 213.7 kΩ, RD = 7.2 kΩ, RS = 1.6 kΩ, and RL = 600Ω. (a) Show that ID = 2.5mA and VDS = 18V. 2