BeginnerTopic 24 of 104Electronics & Embedded
Oscillators
Circuits like Wien bridge and crystal oscillators generate periodic signals.
In depth
Oscillators sustain a periodic signal using positive feedback satisfying the Barkhausen criterion (loop gain 1, phase 0°). RC (Wien bridge, phase shift), LC (Colpitts, Hartley) and crystal oscillators trade stability and frequency range. Relaxation oscillators produce square or triangular waves.
Key points
- Frequency f=1/(2πRC) for Wien
- Quartz crystals ±20 ppm
- Start-up conditions
ExampleA quartz crystal sets the clock of a microcontroller.
Oscillators generate periodic signals for clocks, radios and test equipment, so their frequency stability is a key design requirement.
What is Oscillators?
Circuits like Wien bridge and crystal oscillators generate periodic signals.
Why is it important to understand oscillators?
Oscillators generate periodic signals for clocks, radios and test equipment, so their frequency stability is a key design requirement.
Why use a crystal oscillator?
A quartz crystal has a very high Q and stable resonance, so the frequency is far more accurate and temperature stable than an LC or RC oscillator.
What does the Barkhausen criterion say?
An oscillator needs a loop gain of one with zero net phase shift at the frequency of oscillation.
How is Oscillators used in practice?
Typical applications include building a simple audio tone generator with a Wien bridge, providing a stable clock for a microcontroller with a crystal and creating a carrier signal in a radio transmitter.
What should I learn before Oscillators?
Study "Active filters" first (topic 23 of 104 in Electronics & Embedded). It covers the groundwork this topic builds on.
What are the key points of Oscillators?
Frequency f=1/(2πRC) for Wien. Quartz crystals ±20 ppm. Start-up conditions.
Can you give an example of Oscillators?
A quartz crystal sets the clock of a microcontroller.
What comes after Oscillators?
The next topic is "555 timer", which builds directly on this one.
How difficult is Oscillators?
It is classed as Beginner in Electronics & Embedded (topic 24 of 104). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.