G7 - Practical Circuits

Capacitors and inductors are used in a power-supply filter network. A power-supply bleeder resistor provides discharges the filter capacitors in a power supply acting as a safety feature.

The minimum peak-inverse-voltage rating of the rectifier in a fullwave power supply should be double the normal peak output voltage of the power supply. The approximate minimum peak-inverse-voltage rating of the rectifier in a half-wave power supply should be two times the normal peak output voltage of the power supply.

A Filter is used to process signals from the balanced modulator and send them to the mixer in a single-sideband phone transmitter A Balanced modulator is used to combine signals from the carrier oscillator and speech amplifier and send the result to the filter in a typical single-sideband phone transmitter.

A Mixer is used to process signals from the RF amplifier and local oscillator and send the result to the IF filter in a superheterodyne receiver.

A Product detector is used to process signals from the IF amplifier and BFO and send the result to the AF amplifier in a single-sideband phone superheterodyne receiver.

The impedance of a low-pass filter as compared to the impedance of the transmission line into which it is inserted should be about the same.

The simplest combination of stages that can be combined to implement a superheterodyne receiver is HF oscillator, mixer and detector.

A direct conversion receiver is suitable for CW and SSB reception but does not require a mixer stage or an IF amplifier.

A discriminator is used in many FM receivers to convert signals coming from the IF amplifier to audio.

An advantage of a crystal controlled transmitter is stable output frequency.

An advantage of a switched-mode power supply as compared to a linear power supply is that high frequency operation allows the use of smaller components. A desirable characteristic for capacitors used to filter the DC output of a switching power supply is low equivalent series resistance.

A half-wave rectifier converts AC to DC during 180 degrees of the AC cycle. A full-wave rectifier converts AC to DC during 360 degrees of the AC cycle. The output waveform of an unfiltered full-wave rectifier connected to a resistive load is a series of DC pulses at twice the frequency of the AC input

A “flip-flop” circuit is a digital circuit with two stable states. Digital circuits use the binary number system because binary "ones" and "zeros" are easy to represent with an "on" or "off" state. The output of a two-input NAND gate, given both inputs are “one” is zero. The output of a NOR gate given that both inputs are “zero” is one.

A 3-bit binary counter has 8 states [23 = 8]. A shift register is a clocked array of circuits that passes data in steps along the array.

The basic components of virtually all oscillators are a filter and an amplifier operating in a feedback loop. The phase shift of the RC feedback circuit determines the frequency of an RC oscillator. The inductance and capacitance in the tank circuit determines the frequency of an LC oscillator.

A linear amplifier is an amplifier whose output preserves the input waveform. Low distortion is a characteristic of a Class A amplifier

A Class C power stage is appropriate for amplifying a CW signal. An advantage of a Class C amplifier is high efficiency.

The efficiency of an RF power amplifier is determined by dividing the RF output power by the DC input power.

Questions about six of the components in figure G1-1 appear in the General question pool:

 

Symbol  3=Fixed resistor Symbol  6=Transformer
Symbol  4=NPN transistor Symbol 11=Single pole switch
Symbol  5=Variable capacitor Symbol 13=Single cell battery

 



Figure G7-1