Figure 2.2 The op amp shown connected to dc power supplies.

84 Pages·2017·6.77 MB·English

CHAPTER 11
Feedback
Microelectronic Circuits, Seventh Edition Sedra/Smith Copyright © 2015 by Oxford University Press
Figure 11.1 General structure of the feedback amplifier. This is a signal-flow diagram, and the
quantities x represent either voltage or current signals.
Microelectronic Circuits, Seventh Edition Sedra/Smith Copyright © 2015 by Oxford University Press
Figure 11.2 Determining the loop gain by breaking the feedback loop at the output of the basic amplifier,
applying a test signal x, and measuring the returned signal x : Aβ ≡ −x/x.
t r r t
Microelectronic Circuits, Seventh Edition Sedra/Smith Copyright © 2015 by Oxford University Press
Figure 11.3 (a) A noninverting op-amp circuit for Example 11.1. (b) The circuit in (a) with the op amp
replaced with its equivalent circuit.
Microelectronic Circuits, Seventh Edition Sedra/Smith Copyright © 2015 by Oxford University Press
Microelectronic Circuits, Seventh Edition Sedra/Smith Copyright © 2015 by Oxford University Press
Figure 11.4 Application of negative feedback reduces the midband gain, increases f , and
H
reduces f , all by the same factor, (1 + A β), which is equal to the amount of feedback.
L M
Microelectronic Circuits, Seventh Edition Sedra/Smith Copyright © 2015 by Oxford University Press
Figure 11.5 Illustrating the application of negative feedback to improve the signal-to-interference ratio in amplifiers.
Microelectronic Circuits, Seventh Edition Sedra/Smith Copyright © 2015 by Oxford University Press
Microelectronic Circuits, Seventh Edition Sedra/Smith Copyright © 2015 by Oxford University Press
Figure 11.7 Block diagram of a feedback voltage amplifier. Here the appropriate feedback topology is series–shunt.
Microelectronic Circuits, Seventh Edition Sedra/Smith Copyright © 2015 by Oxford University Press
Figure 11.8 Examples of a feedback voltage amplifier. All these circuits employ series–shunt feedback.
Note that the dc bias circuits are only partially shown.
Microelectronic Circuits, Seventh Edition Sedra/Smith Copyright © 2015 by Oxford University Press