Lecture 24 Oscillators: Steady-State...
Transcript of Lecture 24 Oscillators: Steady-State...
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EE142 Lecture23
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Amin Arbabian
Jan M. Rabaey
Lecture 24
Oscillators:
Steady-State Analysis
EE142 – Fall 2010
Nov. 23rd, 2010
University of California, Berkeley
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Review
Analyzed a multi-pole system with feedback,
derived oscillation conditions
Feedback view of oscillators, condition for
oscillation (gain and phase)
Today we will cover steady-state conditions for
oscillation and look at amplitude limiting
mechanisms….
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Review: LC Oscillator
AC
Small-Signal AC
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Small Signal Equivalent Circuit
With Loading
Loop Gain:
@ Resonance
𝐴𝑙 =𝑔𝑚𝑅
𝑛
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Closed Loop Transfer Function
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Closed Loop Gain vs Al
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Magnitude of the Poles
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Root Locus
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Role of Loop Gain
A
2
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Steady-State Analysis
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Steady-State Waveforms
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Steady State Equations
The input waveform is a scaled version of the output
This implies that:
Or that the loop gain in steady-state is unity and the
phase of the loop gain is zero degrees (an exact multiple
of 2π)
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Large Signal Gm
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Large Signal Gm (2)
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Large Signal Gm (3)
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Stability (Intuition)
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Intuition
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BJT Oscillator Design Procedure
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Design (2)
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Common Base Oscillator
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Colpitts Oscillator
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Colpitts with Bias
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Colpitts Family
If we remove the explicit ground connection on the
oscillator, we have the template for a generic oscillator.
Will come back to this later on (one-port view)
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Common-Emitter and Common-Collector…
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Pierce Oscillator
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Pierce Oscillator with Bias
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Common-Collector Oscillator
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Clapp Oscillator
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Negative Resistance Perspective
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Oscillator Stability
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Negative Resistance LC Oscillator
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Oscillation Condition