18 Questions
What is the primary goal of feedback in an oscillator circuit?
To sustain oscillation
What is a common reason for an oscillator to fail to start?
Low stage gain
What is an advantage of a crystal-controlled oscillator over a VFO?
Single-frequency operation
What is a disadvantage of using discrete components instead of ICs?
Lower component density
Which component is typically not practical for fabrication in an IC?
Inductors
What is the purpose of negative feedback in an op amp?
To control the gain
What is the purpose of comparing the output voltages to the internal voltage divider in a 555 timer?
To trigger the output signal
What is the duty cycle of a signal defined as?
The time the output is active divided by the total period of the output signal
What is the resolution of a digital-to-analog converter (DAC)?
The smallest analog output change that can occur as a result of an increment in the digital input
What is the phenomenon exhibited by a crystal when a mechanical force across the crystal causes a small voltage to be generated?
Piezoelectric effect
What is the formula for determining the time period of a monostable 555 multivibrator?
T = 0.33RC
Which pin of the 555 timer is used to reset the timer?
Pin 4
What type of oscillator is characterized by a split capacitor in its tank circuit?
Colpitts oscillator
Which type of circuit is required for oscillation?
A stage with gain
What is a common classification of filters?
All of the above
What is the purpose of a capacitor in the feedback path of an op-amp circuit?
To act as an integrator
Which oscillator is known for its good frequency stability?
Crystal oscillator
What type of circuit is a phase-selective circuit?
Frequency-selective circuit
Study Notes
Oscillator Circuits
- Feedback in an oscillator circuit should be just enough to sustain oscillation.
- Low power supply voltage, low stage gain, and in-phase feedback can prevent an oscillator from starting.
- Crystal-controlled oscillators have the advantage of single-frequency operation and low drift.
Integrated Circuits (ICs)
- ICs have higher component density, ease of maintenance, and lower current consumption compared to discrete components.
- Inductors are generally not practical for fabrication in an IC.
Operational Amplifiers (Op Amps)
- Op amps usually employ negative feedback to control the gain.
- Op amps compare the input voltages to the internal voltage divider.
555 Timer
- The duty cycle of a 555 timer is defined as the time the output is active divided by the total period of the output signal.
- Pin 1 of the 555 timer is the ground pin.
- Pin 2 is the trigger pin.
- The standard 555 package includes 2 comparators.
- Reset is present at pin 4 of the 555 timer.
Digital-to-Analog Converters (DACs)
- The resolution of a DAC is the smallest analog output change that can occur as a result of an increment in the digital input.
Crystal and Piezoelectric Effect
- A crystal demonstrates the piezoelectric effect when a mechanical force across the crystal causes a small voltage to be generated.
Monostable 555 Multivibrator
- The time period of a monostable 555 multivibrator is T = 1.1RC.
Filters
- A band-reject filter has two stop bands.
- The gain of the first-order low-pass filter decreases at the rate of 20dB/decade.
- An electrical filter is a frequency-selective circuit.
- Filters can be classified as analog or digital, passive or active, and audio or radio frequency.
Oscillators
- The Colpitts oscillator is characterized by a split capacitor in its tank circuit.
- A crystal oscillator is a fixed frequency oscillator.
- The Colpitts oscillator gives good frequency stability.
- Oscillation requires a stage with gain and negative feedback.
- A Colpitts oscillator can be recognized by a split capacitance in the tuned circuit.
Test your knowledge of oscillators in electronics, including common-base arrangements, feedback, and crystal-controlled oscillators.
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