Ch20

What is the total forward current for a germanium food with a 9v external resistor

9-0.3/190 ohm = 0.048

Describe three methods of diode fabrication

A grown junction method , intrinsic semiconductor material and p type impurity

Seed

A small semiconductor

What is the minimum amount of voltage need to produce current flow across a on junction diode

Current flow occurs only if the external voltage is greater than the barrier voltage

Reverse bias

Terminals are reversed, the diode does not conduct it is said to connected

Which method of diode of diode fabrication is favored over the other

The diffused junction methods is the methods most used today

How is the depletion region formed

The electron and holes are depleted

Cathode

The n section

Anode

The p section

Depletion region

The region near the junction where the electron and holes are depleted

Peak inverse voltage or piv

They also specify the maximum -safe reverse voltage

Bias voltage

When voltage is applied to a diode

Maximum forward current

(If max) that can be handled safely

What are typical barrier voltage for germanium and silicon diode

0.3 v for a germanium on and 0.7 for a silicon on junction .

Diode

By joining n and p type material together

What problem can a reverse current create in a germanium or silicon diode

Damaged the by excessive heat and excessive reverse voltage

How does a ohmmeter indicate that a diode of shorted

If a diode shows. Both low forward and low reverse resistance

Why are the diode after fabricated put in a package

If large current are to flow through the diode, the package must be designed to keep the junction from overheating

How does the ohm meter indicate that a diode is open

If the diode measured both high forward and high reverse resistance

What is the leakage current in on junction diode

In germanium diode it is measured micro-amperes; in silicon diodes it is measured on nano peers

Reversed current l

Leakage current

Why should a resistor be connected on series -biased diode

Limit the forward current to a safe value

Junction diode

N and p type material come together

Barrier voltage

Opposing chargers that build up on each side of the junction creat voltage

Doping

Process of adding impurity to pure semiconductor crystal to increase the number of free electron or the number of holes

Forward voltage drop

Voltage is equal to the barrier

What is leakage current in a on junction diode

When it is reversed biased ,only a small leakage current flows.it is this characteristic that allows the diode to be used as a rectifier

Forward bias

When the current flow n -type toward the p-type material