Comprehensive

Question 1

What are the 6 big topics of the course?

Answer 1

• Amplifiers
• Diodes
• rectifiers
• MOSFET DC circuits
• MOSFET amplifiers & small signal analysis
• BJTs

Question 2

Four types of controlled-source amplifiers

Answer 2

Voltage, Current, Transresistance, Transconductance

Question 3

Voltage amplifier (V-type)

Answer 3

Voltage-controlled voltage source (VCVS); output is voltage, input is voltage; gain Av = Vout/Vin (unitless)

Question 4

Current amplifier (I-type)

Answer 4

Current-controlled current source (CCCS); output is current, input is current; gain Ai = Iout/Iin (unitless)

Question 5

Transresistance amplifier (R-type)

Answer 5

Current-controlled voltage source (CCVS); input is current, output is voltage; gain Rm = Vout/Iin (ohms)

Question 6

Transconductance amplifier (G-type)

Answer 6

Voltage-controlled current source (VCCS); input is voltage, output is current; gain Gm = Iout/Vin (siemens or A/V)

Question 7

Main methods to convert between the four amplifier types

Voltage, Current, Transresistance, Transconductance Amplifiers

Answer 7

Ohm’s law and source transformations

Question 8

Example of source transformation: current source in parallel with resistor becomes

Answer 8

Voltage source in series with the same resistor (V = I × R)

Vice Versa works too

Question 9

What happens when you cascade amplifiers?

Answer 9

The output resistance of one stage loads the input resistance of the next; must account for loading to find overall gain

Question 10

Diode device physics: p-type doping

Answer 10

Acceptor doping (boron) → holes are majority carriers

Question 11

Diode device physics: n-type doping

Answer 11

Donor doping (phosphorus) → electrons are majority carriers

Question 12

What forms at a p-n junction with no bias?

Answer 12

Depletion region (layer)

Question 13

Forward bias on a diode: what happens to the depletion layer?

Answer 13

Depletion layer shrinks (goes away with enough current)

Question 14

Reverse bias on a diode: what happens to the depletion layer?

Answer 14

Depletion layer widens

Question 15

Shockley diode equation includes what temperature-dependent term?

Answer 15

Thermal voltage VT ≈ 0.026 V (26 mV) at room temperature

Question 16

Four diode models we used (most accurate → simplest)

Answer 16

Exact (Shockley), Piecewise-linear, Constant voltage drop (0.7 V), Ideal

Question 17

Exact (Shockley) diode model

Answer 17

iD = IS (e^(vD / (n·VT)) – 1); most accurate, exponential characteristic

Question 18

Piecewise-linear diode model

Answer 18

Off: iD = 0 for vD < Vγ; On: vD = Vγ + rd·iD (straight line with small slope rd)

Question 19

Constant voltage drop diode model

Answer 19

Off: iD = 0 for vD < 0.7 V; On: vD = 0.7 V for any positive current (vertical line at 0.7 V)

Question 20

Ideal diode model

Answer 20

Off: open circuit (iD = 0) for vD < 0; On: short circuit (vD = 0) for iD > 0

Question 21

General method for multiple-diode circuits

Answer 21

Assume on/off state for each diode → solve → check consistency with assumptions

Question 22

Zener diodes operate in which region for voltage regulation?

Answer 22

Reverse-breakdown region

Question 23

Three main rectifier topologies we studied

Answer 23

Half-wave, Center-tapped full-wave, Bridge full-wave

Question 24

Ripple voltage and peak diode current are needed to

Answer 24

Specify the filter capacitor value

Question 25

MOSFET has four terminals — name them

Answer 25

Gate, Drain, Source, Body (bulk)

Question 26

MOSFET channel types

Answer 26

n-channel and p-channel

Question 27

MOSFET modes

Answer 27

Enhancement-mode and Depletion-mode

Question 28

Three MOSFET regions of operation

Answer 28

Cutoff, Triode, Saturation

Question 29

In MOSFET analysis, what two voltages do we always check to determine region?

Answer 29

VGS vs Vth and VDS vs (VGS – Vth)

Question 30

Two common DC biasing schemes for MOSFETs we studied

Answer 30

Four-resistor biasing and current-source biasing

Question 31

Key fact about ideal current source in biasing circuits

Answer 31

Voltage across it can be anything; it does not affect the set current

Question 32

Three MOSFET amplifier configurations

Answer 32

Common Source, Common Drain (source follower), Common Gate

Question 33

Small-signal MOSFET model controlled source is

Answer 33

gm · vgs (from drain to source)

Question 34

In small-signal analysis, capacitors are treated as

Answer 34

Open circuit at DC, short circuit at AC (signal frequency)

Question 35

BJT regions of operation

Answer 35

Cutoff, Forward-active (linear), Saturation

Question 36

For BJTs, what is the key thing to remember about current-source biasing?

Answer 36

Voltage on the far side of the current source can be anything and usually can be ignored

Question 37

Overall small-signal analysis procedure

Answer 37

1. Solve DC operating point (DC analysis), 2. Replace devices with small-signal models, 3. Analyze AC circuit

Question 38

Ripple voltage equation for capacitor-filtered full-wave rectifier will be

Answer 38

On the equation sheet (you do not need to derive it)

Question 39

Peak diode current approximation for rectifier design will be

Answer 39

On the equation sheet

Question 40

When finding input/output resistance in MOSFET amplifiers, the only “weird” terminal is

Answer 40

The source → resistance seen is Rsource ∥ 1/gm

Question 41

Common Source amplifier is

Answer 41

Inverting

Question 42

Common Drain (source follower) is

Answer 42

Non-inverting, voltage gain ≈ 1

Question 43

Common Gate amplifier has

Answer 43

Very low input resistance, non-inverting

Question 44

In current mirrors, the voltage across an ideal current source

Answer 44

Does not affect the mirrored current (can be ignored)

Question 45

Current mirror using n-channel MOSFETs on the bottom is called

Answer 45

Current sink

Question 46

Current mirror using p-channel MOSFETs on the top is called

Answer 46

Current source