Week 6

Question 1

How is a field effect transistor constructed?

Answer 1

An FET (field effect transistor) is constructed by placing an insulating layer on top of a silicon wafer

Question 2

What are the two types of FETs?

Answer 2

n-channel and p-channel

Question 3

True or False: FETs are symmetric devices

Answer 3

True

Question 4

What are the names of the three terminals on an FET?

Answer 4

Drain, gate, and source

Question 5

Define metal-oxide-semiconductor FET (MOSFET)

Answer 5

A MOSFET uses a metal plate at the gate to generate an electric field across an insulating layer (oxide) into the semiconductor substrate. This electric field helps (or hinders) the flow of current

Question 6

Define enhancement-type MOSFET

Answer 6

A MOSFET that uses the generated electric field to increase current flow (or “turn on”)

Question 7

Define depletion-type MOSFET

Answer 7

A MOSFET that uses the generated electric field to decrease current flow (or “turn off”)

Question 8

Define a junction FET (JFET)

Answer 8

A JFET uses a reverse-biased pn-junction at the gate to create a depletion region between the source and the drain. This depletion region helps (or hinders) the flow of current

Question 9

True or False: JFETs are enhancement-type FETs

Answer 9

False, the gate in a JFET is used to “turn off” the device

Question 10

True or False: You can mess up a JFET circuit by accidentally forward-biasing the gate pn-junction

Answer 10

True

Question 11

True or False: A FET has various modes of operation depending on the voltages at its terminals

Answer 11

True

Question 12

True or False: A MOSFET is in saturation region when The drain-source voltage is just below the overdrive voltage

Answer 12

False, it’s in saturation when the drain-source voltage is above the overdrive voltage

Question 13

Define overdrive voltage

Answer 13

The gate-source voltage minus the threshold voltage

Question 14

True or False: A MOSFET has zero gate current

Answer 14

True

Question 15

True or False: A MOSFET in the triode region often dissipates significantly higher power than in the saturation region

Answer 15

False, other way around is True

Question 16

True or False: A MOSFET in triode region acts like a gate-controlled variable resistor

Answer 16

True

Question 17

True or False: A transistor can be used as an amplifier

Answer 17

True

Question 18

What order (highest to lowest) would the following circuit elements rank in terms of amplifier gain? BJT, JFET, or a MOSFET

Answer 18

BJT, JFET, MOSFET

Question 19

What order (largest to smallest) would the following circuit elements rank in terms of amplifier frequency range? BJT, JFET, or a MOSFET

Answer 19

BJT, JFET, MOSFET

Question 20

What order (largest to smallest) would the following circuit elements rank in terms of leakage current (base-gate current)? BJT, JFET, or a MOSFET

Answer 20

BJT, JFET, MOSFET

Question 21

What order (fastest to sowest) would the following circuit elements rank in terms of switching speed? BJT, JFET, or a MOSFET

Answer 21

BJT & JFET (tied), MOSFET

Question 22

What order (highest to lowest) would the following circuit elements rank in terms of heat tolerance? BJT, JFET, or a MOSFET

Answer 22

MOSFET, JFET & BJT (tied)