Electrical Control Devices and Semiconductors

Flashcards about electrical control devices and semiconductors.

What is the function of diodes?

allow current flow in only one direction

What does 'Di' mean in the term 'Diode'?

Two

What are the connections in a diode called?

Anode (+) and cathode (-)

What are modern diodes known as?

Semiconductor diodes or solid-state diodes

Under what condition do electrons flow in a diode?

If the voltage at the anode is positive with respect to the cathode (Forward-biased)

What is a crystal or crystalline solid?

A solid material whose atoms, molecules, or ions are arranged in an orderly repeating pattern.

What is doping?

To control the conductivity of the semiconductor, the silicon and germanium crystals are doped with impurity atoms

What is N-Type semiconductor?

A semiconductor with a donor impurity (negative ion)

What is P-Type semiconductor?

A semiconductor with an acceptor impurity (positive ion).

What happens when a single crystal containing N-type and P-type regions is manufactured?

A P-N junction where the two crystals are joined.

What is the barrier layer in a P-N junction?

Electrons in the N-type material adjacent to the junction fill the holes in the P-type material adjacent to the junction.

What happens when the negative terminal is connected to the P-type material and the positive terminal to the N-type in a P-N junction?

Barrier width increases and no current flows (Negative or reverse bias)

What is a Zener diode?

A diode designed so that the breakdown occurs at a defined voltage

What does the arrow indicate on diode symbols?

The direction of conventional current flow when the diode is forward biased

How is the cathode often indicated on diode components?

As either a black band on a light background or a white band on a dark background.

What is the main purpose of Zener diodes?

Voltage stabilizing.

How can diodes be used in rectification?

To change AC into DC.

What is the function of a half wave rectifier?

Removes the negative alternation.

What is a key characteristic of a bridge rectifier?

The voltage across the load is always positive.

How can a diode be tested?

Using special diode testers or a multimeter.

What does a low resistance reading on a multimeter indicate when testing a diode in forward bias?

Indicates the diode is working

How is a high resistance typically displayed on a multimeter when reverse biasing a diode?

A 1 or OL (Out of Limits)

What is the consequence of an open diode?

Extremely high resistance value in both forward and reverse bias

What occurs in the case of a shorted diode?

Extremely low resistance value in both forward and reverse bias

What is the result of forward biasing of Light Emitting Diodes?

Emit some form of light energy when forward biased.

What are two basic function of transistors?

Switching and amplifying

What is the function of Emitter in Transistors?

supplies a large number of majority carriers for the current to flow through the transistor

What does 'Active region' mean for transistors?

the transistor is typically operated in this region for amplifying purposes. In the active region changes in collector current are controlled by changes in the base current

What does 'Saturation region' mean for transistors?

here small changes in collector voltage will result in substantial changes in the collector current.

What does 'Breakdown region' mean for transistors?

this area of the transistor curve above approx. 40V. The transistor should not be operated in this region since it will most likely damage the semiconductor material.

What is Gain represented by?

represented by the Greek letter β Gain = Collector current/Base current β = IC/IB

What is the function of Silicon Controlled Rectifier?

Can be used to reduce current flow through a circuit by reducing the amount of time current flows.

What are the three terminals of SCR?

Anode (A), Cathode (C), Gate (G)

How to stop the flow of current in SCR?

To stop the flow of current the voltage source must be removed (turned off).