Transistors

Question 1

What are the 2 basic categories of transistors?

Answer 1

Bipolar Junction Transistor and Field Effect Transistor.

Question 2

What is considered a current controlled device?

Answer 2

BJT

Question 3

What is considered a voltage controlled device?

Answer 3

FET field effect transistor, JFET, MOSFET

Question 4

Explain the collector on a BJT

Answer 4

Relatively large, weakly doped region, size reduces resistance as this are generates the largest amount of heat.

Question 5

Describe the emitter part of a BJT

Answer 5

Strongly doped, same type as the collector

Question 6

How can you tell which transistor is the NPN?

Answer 6

Not point in, the arrow on the symbol is pointing away from the base.

Question 7

The arrow on the BJT transistor symbol indicates?

Answer 7

It is always attached to the emitter leg.

Question 8

What are the names of the 3 terminals on a FET transistor?

Answer 8

Drain, Source and Gate

Question 9

On an FET what is the drain and source used for?

Answer 9

They are normally connected to the power supply through the source and drain terminals.

Question 10

What is the gate used for in an FET?

Answer 10

An input signal to be amplified.

Question 11

Devices that use reverse-biased junction isolation are called?

Answer 11

Junction FET’s, Jug FET JFETS.

Question 12

What are the 2 basic categories of FET’s

Answer 12

Reverse biased PN junctions and isolation provided by an electrically insulating material.

Question 13

Devices that use insulating materials are called?

Answer 13

Metal oxide semiconductors MOSFET, Insulated gate IGFET

Question 14

What is mainly used in todays integrated circuits?

Answer 14

MOSFETS

Question 15

What are the modes of operation and which transistor operates where?

Answer 15

MOSFET - Enhancement mode & Depletion
JFETS - Depletion mode only.

Question 16

Describe enhancement mode of a MOSFET

Answer 16

Increased voltage applied to gate increases conductivity of the channel, this allows more current to flow from drain to source or vice versa.

Question 17

Explain depletion mode of a MOSFET

Answer 17

The transistor is “ON” by default and allowing current to flow, When a voltage is applied to the gate conductivity is reduced and can even turn the transistor OFF, like opening a switch

Question 18

What controls the current flow of a JFET

Answer 18

Voltage connected to the gate controls the depletion region.

Question 19

How does the JFET work?

Answer 19

By applying a reverse bias voltage to a gate terminal, at this point the channel is squeezed and the electric current is impeded or switched off completely.

Question 20

How many connections does a MOSFET have?

Answer 20

3

Question 21

The gate is insulate from the channel on a MOSFET by what material?

Answer 21

Thin film of silicon dioxide.

Question 22

On a MOSFET, what connects the drain to the source?

Answer 22

The channel material.

Question 23

Depletion type MOSFETS can be operated in what modes?

Answer 23

Depletion or in enhancement.

Question 24

What controls current flow through the channels on a MOSFET?

Answer 24

Gate voltage controls current flow.

Question 25

What happens when a + voltage is applied to the gate of a MOSFET?

Answer 25

The channel size increases/enhances increasing current flow from source to drain.

Question 26

What happens when a higher negative voltage is applied to the gate of a MOSFET?

Answer 26

The MOSFET acts in depletion mode reducing the source to drain current.

Question 27

What functions can the BJT be used as?

Answer 27

Amplifier or a switch

Question 28

Explain gain

Answer 28

A transistor can use a small signal applied between one pair of its terminals to control a much larger signal at another pair of terminals.

Question 29

How does a transistor perform as a amplifier.

Answer 29

By the use of a small signal applied between one pair of its terminals, which controls a much larger output between the other 2 terminals.

Question 30

How is a BJT current controlled?

Answer 30

Voltage is applied to base, therefor a VOLTAGE and a CURRENT is applied. however the voltage only performs up to sufficient voltage which creates forward bias across the base emitter junction. past this point current increases making current the controlling factor of a BJT.