Anthony Li Alec Wasowicz HKN ECE 342 Review Session 1 Anthony Li Alec Wasowicz

MOSFET’s NMOS PMOS

MOSFET Operating Point Three regions of operation: Cutoff (VGS < VT): ID = 0 Linear/Triode (VGS > VT, VDS < VGS - VT): 𝐼𝐷 = 𝜇𝑛𝐶𝑜𝑥( 𝑊 𝐿 )(( 𝑉 𝐺𝑆 − 𝑉 𝑇 ) 𝑉 𝐷𝑆 − 𝑉 𝐷𝑆 2 2 ) Saturation (VGS > VT, VDS > VGS - VT): 𝐼𝐷 = 𝜇𝑛𝐶𝑜𝑥 𝑊 𝐿 ½ 𝑉𝐺𝑆 − 𝑉 𝑇 2 (1+ λ 𝑉 𝐷𝑆 ) Note: 𝜇 𝑛 𝐶 𝑜𝑥 𝑊 𝐿 = 𝑘 ′ 𝑊 𝐿 =𝑘

MOSFET Incremental Model Transconductance: 𝑔 𝑚 = 2 𝐼 𝐷 𝑉 𝑂𝑉

Gain Calculation Av = -GMRout GM = Short Circuit small signal transconductance, ratio of iout to vin ROUT = Equivalent incremental output resistance

Common Amplifier Topologies Diode-tied Transistor What is overdrive voltage here? Is this always in saturation? Common Source/Drain/Gate Purpose of each topology? equations Common Source with Degeneration Cascode Diode Tied Transistor

Common Source/Drain/Gate ROUT = RD || rds Gm = gm ROUT = RS || (rds || 1/gm) Gm = - gm ROUT = RD || rds Gm = - gm Common Source. Your basic amplifier topology. Notice the infinite input resistance and inverted gain. Common Drain. Also known as a level shifter. These make great buffers. Source follower? Common Gate. good current buffer i believe.

Degeneration When a resistance is “viewed” through the drain, it appears bigger by a factor related to the transconductance. 𝑅𝑂𝑈𝑇 = 𝑅𝐷 || (𝑟𝑑𝑠 + 𝑅𝑆 + 𝑔𝑚𝑟𝑑𝑠𝑅𝑆) 𝐺𝑚 = 𝑔𝑚 1 + 𝑔 𝑚 𝑅 𝑆 Note that these formulas simplify to the common source ones if Rs is zero. Also remember that these equations rely on rds not being infinity.

Cascode Similar to degeneration but GM is not attenuated 𝐺 𝑀 = 𝑔 𝑚1 𝑅 𝑜𝑢𝑡 = 𝑟 𝑑𝑠2 + 𝑟 𝑑𝑠1 +𝑔 𝑚 2 𝑟 𝑑𝑠2 𝑟 𝑑𝑠1

Fall 2016 Midterm 2 Problem 1

Fall 2017 Midterm 2 Problem 3

Fall 2017 Midterm 2 Problem 3

Homework 5 Problem 3 Part I Find AV

Homework 6 Problem 2 Part F