oscillator circuits. outline oscillators – inverter-based oscillator – introduction of phase...

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Oscillator Circuits

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Page 1: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Oscillator Circuits

Page 2: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Outline

• Oscillators– Inverter-Based Oscillator– Introduction of Phase Noise Simulation– LC-Tank Based Oscillator• Laplace Analysis• Circuit Implementation• Quality Factor Analysis

Page 3: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Inverter-Based Oscillator

Page 4: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Delay Per Stage of the Inverter(273 pS) (395 ps)

Period: 395-273=122 pS, Delay per stage (TD): 234-214=20 pS. Period is 2NTD

Page 5: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Oscillation Frequency Calculation

• fosc=2.14 GHz

• Tosc=467 pS=2NTD

– TD=20 pS

– N=Tosc/(2TD)=467 pS/(2 20)=11.68

– N must be odd. – Choose N as 11.

Page 6: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

11 Stage Oscillator

Page 7: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

11 Stage Oscillator

Period: 1.501 nS-1.052 nS=0.449 nS, Freq=2.227 GHz

Page 8: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Phase Noise

Page 9: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Periodic Steady State Analysis

Page 10: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Harmonics

Page 11: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Pnoise

Page 12: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Phase Noise of a Ring Oscillator

Page 13: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

LC Tank Oscillator

Page 14: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Laplace Transform Analysis

Page 15: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

LC Tank Oscillator

• Resonant Frequency: 2.14 GHz• L=1 nH• C=5.53 pF (Adjustable)

Page 16: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

LC Tank Oscillator

Page 17: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Transient Simulation

(Steady state after 10 nS)

Frequency: 1.941GHz

Page 18: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Reduce the Value of Capacitor

(2.16 GHz)

Page 19: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

PSS and Pnoise Setting

Page 20: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Phase Noise

Page 21: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Quality Factor of 10 for the inductor

Oscillation dies out since gtank is greater than gm of the transistor.

Page 22: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Rind=100 mΩ

This is the maximum parasitic resistance we can have without destroying the oscillation.

Page 23: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Transient Simulation

Page 24: Oscillator Circuits. Outline Oscillators – Inverter-Based Oscillator – Introduction of Phase Noise Simulation – LC-Tank Based Oscillator Laplace Analysis

Phase Noise with Rind=100 mΩ

Even a little series resistance at unreasonably high Q (130) can degrade phase noise quickly.