Environmental Engineering Reference
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in which subscript “ fl ” stands for linear
feedback.
By inspection of (7.17) we see that for amplifiers where coefficient
is
negligible, the third harmonic is still determined by
Moreover, the third
harmonic distortion can be minimised if
and for
(7.17) and (7.18) simplify to
7.1.2 Nonlinear Amplifier with Nonlinear Feedback
When also the feedback network is made up of active components (for
instance, when MOS transistors working in triode region are employed as
feedback elements instead of pure linear resistances, [IF94]), the feedback
network cannot be considered ideally linear as previously done. Evaluation
of the distortion of a feedback amplifier where both the amplifier and the
feedback network introduce substantial nonlinearities was carried out in
[PP981], and is developed in the following.
First, consider the nonlinear behaviour of the feedback path according to
The input signal,
can be written as
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