Week 10
Oscillators and Startup Conditions
I study differential stages, feedback, filters, and output stages as one connected signal path.
What I connect in this unit
An oscillator closes an amplifier around a frequency-selective network. The Barkhausen phase and gain conditions describe steady oscillation, startup needs loop gain slightly above one, RC or LC elements set frequency, and amplitude limiting stops growth.
Concept map
- Barkhausen criterion
- RC oscillators
- LC oscillators
- Amplitude limiting
Technical anchor
With equal R and C in a Wien bridge, f0 = 1/(2πRC) and feedback is one third, so amplifier gain must settle near three.
How I review it
Choose R and C for a target frequency, calculate the frequency range from tolerances, and distinguish startup gain from the steady-state gain imposed by the limiter.
Connection to the full course
Unit 10 of 12. Unit numbers follow concept dependencies rather than the historical lecture calendar.