Chapter 2.1 Diode application

Question 1

Define a diode.

Answer 1

A diode is a semi-conductor device with a single on junction and metal connections to leads. It has the ability to pass current in only one direction.

Question 2

The type of material of a diode?

Answer 2

Semi-conductor

Question 3

The example of semi-conductor a diode use.

Answer 3

A diode usually use a Silicon.

Question 4

What is the p region called?

Answer 4

Anode

Question 5

What is the n region called?

Answer 5

Cathode

Question 6

What are the regions connected to?

Answer 6

To the conductive terminal

Question 7

Draw the basic structure and schematic symbol of a diode.

Answer 7

Draw it on a paper and make sure you know all the labels.

Question 8

What is a semi-conductor?

Answer 8

Semi-conductors are between conductors and insulators in their ability to conduct electricity.

Question 9

What do you call the region that is between the pn junction?

Answer 9

Depletion region

Question 10

Name the examples of Typical Diode packages.

Answer 10

DO - 14 , DO - 21 ,60 - 01

Question 11

Marked by a band, a tab or some other feature.

Answer 11

Cathode

Question 12

What shows the typical diode packages surface mounting on a printed circuit board?

Answer 12

Surface - Mount Diode Packages

Question 13

Types of Surface - Mount Diode Packages

Answer 13

SOT, SMA and SOD

Question 14

What is an SOT type?

Answer 14

The SOT type is a

three-terminal package in which there are either one or two diodes.

Question 15

Name the L- shaped Diode Package.

Answer 15

SMA

Question 16

Name the Gull-wing shaped leads Package .

Answer 16

The SOD and SOT packages

Question 17

Define Forward-bias.

Answer 17

Forward bias is the condition that allows

current through the pn junction.

Question 18

What does it mean to bias a diode.

Answer 18

To bias a diode, you apply a dc voltage across it

Question 19

Another term for DC voltage source

Answer 19

An external bias voltage

Question 20

What is the external bias voltage designed as?

Answer 20

V bias

Question 21

Explain why a series resistor is necessary when a diode is forward-biased.

Answer 21

The resistor limits the forward cur-

rent to a value that will not damage the diode

Question 22

Explain how to forward-bias a diode.

Answer 22

The first requirement is that the negative side of VBIAS is con-
nected to the n region of the diode and the positive side is connected to the p region.

The Second Requirement is that the bias voltage, VBIAS,
must be greater than the barrier potential.

Question 23

What are the two conditions under which a diode is operated?

Answer 23

forward bias and reverse bias

Question 24

Explain The Effect of Forward Bias on the Depletion Region

Answer 24

As more electrons flow into the
depletion region, the number of positive ions is reduced. As more holes effectively flow
into the depletion region on the other side of the pn junction, the number of negative ions
is reduced. This reduction in positive and negative ions during forward bias causes the de-
pletion region to narrow.

Question 25

Define barrier potential.

Answer 25

The electric field between the positive and negative ions in the depletion region on either side of the junction creates an “energy hill” that prevents free electrons from diffusing across the junction at equilibrium.

Question 26

Effect of the Barrier Potential During Forward Bias

Answer 26

When a diode is forward-biased, the external bias voltage provides energy to the free electrons so that they can overcome the barrier potential. Now, these electrons give up an amount of energy equal to the barrier potential when they will cross the depletion region.

Question 27

Define dynamic resistance

Answer 27

The internal resistance which is usually ignored since it’s very small. 

Question 28

Define the Reverse bias

Answer 28

Reverse bias is the condition that essentially prevents current through the diode.

Question 29

Define avalanche effect as applied to diodes.

Answer 29

The multiplication of the conduction with a high reverse bias voltage

Question 30

FORWARD BIAS: PERMITS MAJORITY-CARRIER CURRENT

Answer 30

■ Bias voltage connections: positive to anode (A); negative to cathode (K). ■ The bias voltage must be greater than the barrier potential. ■ Barrier potential: 0.7 V for silicon. ■ Majority carriers provide the forward current. ■ The depletion region narrows.

Question 31

REVERSE BIAS: PREVENTS MAJORITY-CARRIER CURRENT

Answer 31

■ Bias voltage connections: positive to cathode (K); negative to anode (A). ■ The bias voltage must be less than the breakdown voltage. ■ There is no majority carrier current after transition time. ■ Minority carriers provide a negligibly small reverse current. ■ The depletion region widens.

Question 32

What would you expect to see displayed on an oscilloscope connected across RL in the limiter

Answer 32

The diode is forward-biased and conducts when the input voltage goes below -0.7V so for the negative limiter determine the peak output voltage across RL. Vp(out) = (RL/R1+RL)Vp(in)

Question 33

When does reverse breakdown occur in a diode?

Answer 33

When it exceeds the breakdown voltage of the diode