chapter 3 components & units

Chapter 3Components & Units

04/21/23 11 July 2010-30 June 2014 Technician

Diodes, Transistors and Integrated Circuits

Resistors, capacitors and inductors treat the values and polarities of voltage and current the same.

Other components depend on the polarity and value of voltage and current.

Additionally, some materials don’t conduct electricity as well as a metallic conductor nor are they a good insulator.

We call these materials “semiconductors”.




Some semiconductors, such as silicon, add small amounts of certain impurities. This is called “doping” and it changes the ability of semiconductors to conduct current.

Depending on the type of impurities used, the result is “N-type” or “P-type” materials.




When N-type and P-type materials are in contact with each other, the result is a “PN Junction” that conducts better in one direction than the other.

P-Type N-Type

CathodeAnode

+Junction

Field




A semiconductor that only allows current to flow in one direction is called a “diode”.

Heavy duty or large diodes are called “rectifiers”. Used in power supplies and power conversion units.

An ac voltage applied to a diode results in a unidirectional, varying or pulsing dc current.




A diode has two electrodes – An “Anode” and a “Cathode”. The cathode is indicated by a stripe. Current flows from anode to cathode.

Cathode

Anode



A special type of diode gives off light when current flows through it. These are called “Light Emitting Diodes” or “LEDs”

The material from which the LED is made determines the color of light that is emitted.

LEDs are most often used as visual indicators.

Because LEDs require less power, they are used in place of incandescent indicator lamps.



Transistors are made from patterns of N- and P-type material. The patterns form structures that allow the transistor to use small voltages and currents to control larger ones.

With the appropriate external circuit and a source of power, transistors can amplify or switch voltages and currents.

Using small signals to control larger signals is called “gain”.



There are two common types of transistors:

Bipolar Junction Transistors (BJT)

Field-effect Transistors (FET)



The BJT is made from three alternating layers of N- and P-type materials and there are types based on the layer arrangement of the materials.

NPN

PNP

The electrodes are called the:

• “base”,

• “emitter” and

• “collector”.

B

B

E

E

C

C



The FET is constructed as a conducting path or channel of N- or P-type material. The ends of the channel form the “source” and “drain” electrodes. The “gate” electrode is used to control current through the channel.



An integrated circuit (IC or “chip”) is made of many components connected together and packaged as a single component.

=



A brief history of how we got here

1st Gen

3rd Gen2nd Gen Small = <100 transistors

Med = 100-1000



5th Gen

Large = 1000-10k transistorsVL = 10k-1M transistors

4th Gen

Over 1 million transistors



The trend continues largely unabated, with chips introduced in 2007 containing tens of billions of transistors.



Protective Components

Protective components are used to prevent equipment damage or safety hazards such as fire or electrical shocks caused by equipment malfunction.

Fuses interrupt excessive current flow by belting a short length of metal. When the metal melts the current path is broken and power is removed from the circuits affected.



Protective Components

Circuit breakers are automatically-operated electrical switches designed to protect an electrical circuit from damage caused by overload or short circuit. When it detects a fault condition it “trips” and immediately discontinues electrical flow.

Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.



Fuses



Circuit Breakers

GFCICircuit Breaker Circuit Breaker Panel



Use properly sized fuses and circuit breakers.

Never replace a fuse or circuit breaker with one of a larger current rating.

Fix the problem instead of trying to work around the problem.



“Surge protectors” limit temporary voltage transients above normal ranges. The effectively become a resistor and dissipate the energy as heat.

“Lightning arrestors” perform a similar function but involving the much higher voltages and currents of a lightning strike.



Circuit Gatekeepers

Switches and relays are simple components that control current through a circuit by connecting and disconnecting the paths that current can follow.

• Opening the circuit interrupts the flow of current.

• Closing the circuit allows the current to flow.

A switch is operated manually while a relay is a switch that is controlled by an electromagnet.


Switches and relays are described by their number of “poles” and “throws”.

• Each pole controls the path of one current.

• A “single pole” (SP) switch controls a single current path.

• A “double pole” (DP) switch controls two separate current paths.



Each throw refers to a different path for the current.

A “double throw” (DT) switch can route current through either of two paths while a “single throw” (ST) switch can only open or close a single path.

The combination of poles and throws describes the switch.

SPST – Single pole, single throwDPST – Double pole, single throwDPDT – Double pole, double throw



Indicators and displays are important components for radio equipment. An “indicator” usually tells you if something is on or off. Meters provide information as a value in the form of numbers or on a numeric scale.

Indicators and meters are often combined in a display on the front panels of many radios.



Schematics and Component Symbols

In order to describe complicated circuits, engineers have developed the “schematic diagram” or simply “schematic”.

Schematics create a visual description of a circuit by using standardized symbols for electrical components called “circuit symbols”.



Schematics and Component Symbols

A schematic does not illustrate the physical layout of a circuit. It only shows how the components are connected electrically.

The lines drawn between components represent the electrical connection.

Each line does not necessarily correspond to a physical wire – it just indicates that an electrical connection exists.



Each component in a schematic is assigned a unique designator.

• Resistors are designated with “R” • Capacitors are designated with “C”• Inductors with “L”• Diodes with “D”• Transistors with “Q”

The first resistor used is designated R1; the second is R2; the third is R3, etc.




Symbols you need to know

+

-

Multi Cell Battery

Single Pole Single Throw (SPST) Switch

Anode

Cathode

Capacitor

Diode



Variable Inductor Adjustable Resistor orPotentiometer “Pot” Antenna

Fixed Resistor

TransformerLAMP



What does component 1 represent?

A resistor or a fixed resistor




A transistor (NPN)




A lamp




A battery or a multi-cell battery




A capacitor or a fixed capacitor




A light emitting diode




A variable resistor




A transformer




A variable inductor




An antenna

Chapter 3Types of Radios & Radio Circuits


We use block diagrams to describe the various states that comprise basic stages of radio transmitters and receivers.

In the early days of radio, amateurs used a separate transmitter and receiver which shared an antenna.

The operator used a switch to connect the transmitter to the antenna and then to the receiver to hear the other station’s response.



Oscillator Driver

TelegraphKey

PowerAmplifier

The oscillator circuit generates a low-power signal with a steady frequency. The next stage of the transmitter is the “driver” which is an amplifying circuit that makes the signal stronger. The “power amplifier” increases the signal strength so other stations can hear the signal. The telegraph key turns the output signal on and off to create Morse code characters.

A simple CW transmitter



“Filters” are circuits that perform very important functions in radio (e.g., reject unwanted signals and noise).

“Passive filters” are made from resistors, inductors and capacitors. Tuned circuits are common examples.

“Active filters” are circuits that contain amplifiers.

Reducing a signal’s strength is called “attenuation”. A filter circuit rejects unwanted signals by attenuating them.



The name of the filter describes what it does with respect to signals.

High-pass – a filter that attenuates signals below a specified cutoff frequency. Allows signals above the cutoff frequency to be heard.

Low-pass – A filter that allows signals below a specified cutoff frequency to be heard and rejects signals above the cutoff frequency.



Band-pass – a filter that rejects signals above and below specified cutoff frequencies. Allows signals between the cutoff frequencies to be heard.

Notch – opposite of the band-pass filter. It rejects signals between the cutoff frequencies and allows the frequencies above and below the cutoff frequencies to be heard..



“Modulation” is the process of combining data or voice signals with an RF signal.

A circuit that performs the modulation function is called a “modulator”.

When the modulator circuit does its job, the result is an RF signal that can be communicated via radio.



“Mixers” are closely related to modulators.

Both types of circuits combine signals with the intent of producing an output signal with a different frequency.

The mixer combines two RF signals. It does not combine a data or voice signal with an RF signal.

Mixers are used in transmitters and receivers to shift signal frequencies for various purposes.



“Demodulators” are circuits that separates the data or voice from an RF signal.

Several methods of demodulation can be used so demodulator is a general term that is applied to the many different types of circuits used for demodulation.

“Detectors” are one category of demodulators. A detector converts a modulated RF signal directly into a data or voice signal.



“Product Detectors” detect CW and SSB signals by combining a signal at the frequency of the modulated signal’s RF carrier with the modulated signal itself.

For CW signals, the output of the product detector is an audio reproduction of the Morse code pattern.

For SSB signals, the output is the reproduced data or speech signal.



A “frequency discriminator” or “discriminator” is used to recover information from an FM signal.

A discriminator translates the variations of the FM signal’s frequency back to the original signal used to modulate the RF signal.



Filter MixerAmplifier

or DSP

LocalOscillator

ModulatingSignal

Direct-conversion receivers are the most common receiver used today (if you include mobile phones). They covert modulated signals directly back to speech or data. A filter removes unwanted signals. Digital signals are converted using digital signal processing (DSP) techniques.



The “superheterodyne receiver” is the standard in amateur radio. The key characteristic of the “superhet” is the use of mixers to shift incoming signals of any frequency to a single fixed frequency called the “intermediate frequency” or “IF”.

Unwanted signals can be rejected by narrow filters. An “IF amplifier” then amplifies the desired signal so it can be demodulated and the information recovered.



MixerIntermediate

FrequencyAmplifier

Product Detector

AudioAmplifier

Oscillator BeatFrequencyOscillator

A superheterodyne receiver

The “product detector” follows the IF amplifier allowing CW or SSB signals to be recovered. The BFO can be adjusted to produce different tones or frequencies in the output signal.



MixerIntermediate

FrequencyAmplifier

Product Detector

AudioAmplifier

Oscillator BeatFrequencyOscillator

A superheterodyne receiver

Because there is only one mixer and IF in this receiver, it is a “single-conversion superheterodyne”. Some receivers use “double-conversion” or even “triple-conversion”.



MixerIntermediate

FrequencyAmplifier

LimiterAudio

Amplifier

Oscillator

DiscriminatorRF

AmplifierWideFilter

An FM Superheterodyne Receiver

In this receiver the FM signal is sent to the “Limiter” where all amplitude variations are removed. The output of the limiter is applied to the discriminator to recover the voice signal that is amplified and heard on a speaker.



Receivers are compared on the basis of “sensitivity” and “selectivity”.

Receiver sensitivity determines its ability to detect weak signals.

If a receiver is not sensitive enough, a “preamplifier” or “preamp” can be used. The preamp is connected between the receiver and the antenna.

Selectivity is the ability of the receiver to retrieve the information from the desired signal in the presence of unwanted signals.



Transverters

The superheterodyne technique of shifting signal frequencies can be applied at the equipment level to allow a transceiver to operate on a band other than it was designed for.

Instead of a mixer, a “transverter” is used. Low power signals on one band are shifted to a new output frequency where they are amplified for transmission.



Transverters

Transverters are used by hams to allow one main transceiver to be used on one or more “new” bands.

Few transceivers are available for CW and SSB operations on 222 MHz. A transverter is used to convert 222 MHz signals to and from the 28 MHz band which is on all HF gear.



Questions?

Read Chapter 4 for the next class session.

chapter 3 components & units

Documents

components units

ptype materials

type of impurities

power conversion units

integrated circuitswhen

materials semiconductors

current flows

common types of transistors