Extra exam: practical circuits
Amplifiers, filters, mixers, oscillators, DSP and power supplies. 88 questions, 10 at a time, starting with ones you haven't seen.
Rules to remember10 key practical circuits rulesShow the rules
- A decade counter counts ten input pulses and then produces one output pulse, dividing by ten. (p. 72)
- An OR gate outputs a 1 when any of its inputs is 1. (p. 73)
- In positive logic, the higher voltage stands for a 1 and the lower voltage for a 0. (p. 74)
- Shape factor compares a filter's bandwidth at two attenuation levels, showing how well it rejects nearby signals. (p. 78)
- A balanced modulator produces a double-sideband suppressed-carrier signal, and a filter then removes one sideband to leave SSB. (p. 81)
- A mixer's output contains the two input frequencies plus their sum and their difference. (p. 82)
- Input offset voltage is the small differential input needed to bring the open-loop output to zero. (p. 86)
- The gain-bandwidth figure is the frequency where the op-amp's open-loop gain falls to one. (p. 86)
- The Colpitts, Hartley and Pierce circuits are three widely used oscillator designs. (p. 88)
- NP0 capacitors barely change value with temperature, so they reduce thermal drift in crystal oscillators. (p. 89)
Taken from the explanations to checked practice questions; page numbers link to the official handbook.
Sample practical circuits questions
1.What is characteristic of an emitter follower (or common collector) amplifier?
- ALow input impedance and phase inversion from input to output
- BActs as an OR circuit if one input is grounded
- CInput and output signals in-phase
- DDifferential inputs and single output
Show the answer
✓ C. Input and output signals in-phase
An emitter follower has gain just under one, and its output follows the input in phase.
2.What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital-to-analog converter, and a low-pass anti-alias filter?
- AA hybrid synthesizer
- BA direct digital synthesizer
- CA direct conversion synthesizer
- DA phase-locked loop synthesizer
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✓ B. A direct digital synthesizer
A direct digital synthesizer uses a phase accumulator, a waveform lookup table, a D/A converter and a low-pass filter.
3.What is meant by the term "baseband" in radio communications?
- AThe unmodulated bandwidth of the transmitted signal
- BThe lowest frequency band that the transmitter or receiver covers
- CThe frequency range occupied by a message signal prior to modulation
- DThe basic oscillator frequency in an FM transmitter that is multiplied to increase the deviation and carrier frequency
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✓ C. The frequency range occupied by a message signal prior to modulation
Baseband is the frequency range the message signal, such as audio or data, occupies before it modulates a carrier.
4.What is meant by the term "op-amp input offset voltage"?
- AThe differential input voltage needed to bring the open loop output voltage to zero
- BThe potential between the amplifier input terminals of the op-amp in an open loop condition
- CThe difference between the output voltage of the op-amp and the input voltage required in the immediately following stage
- DThe output voltage of the op-amp minus its input voltage
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✓ A. The differential input voltage needed to bring the open loop output voltage to zero
Input offset voltage is the small differential input needed to bring the open-loop output to zero.