Comparison: Telescopic Op-Amp with Current Mirror and Fully - - PowerPoint PPT Presentation

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IIT-Bombay Lecture 29 M. Shojaei Baghini

Comparison: Telescopic Op-Amp with Current Mirror and Fully Differential Telescopic Op-Amp

• No effective mirror pole in circuit II
• Effect of poles at nodes N and K (in

the cascode active load)?

Circuit II Circuit I

Mirror pole in circuit I

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IIT-Bombay Lecture 29 M. Shojaei Baghini

Compensation

• Compensation of single-stage op amps can be

achieved by controlling the location of the dominant pole.

• What about two-stage op amps? For example

two dominant poles in fully differential two- stage op amp (given in the next side).

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IIT-Bombay Lecture 29 M. Shojaei Baghini

Two-Stage Op-Amp

• Providing more gain, compared to single-stage

amplifiers (gain can reach to order of (gm × ro )3

• Isolating gain and swing stages
• More convenient for feedback configurations
• First stage has more gain than the second stage.

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IIT-Bombay Lecture 29 M. Shojaei Baghini

Compensation of Two-Stage Op Amp

PE PA PX

PE PA PX

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IIT-Bombay Lecture 29 M. Shojaei Baghini

Pole Splitting with Miller Compensation