Environmental Engineering Reference
In-Depth Information
Substituting (3.9), (3.11) and (3.12) in (3.7), we get
which gives exactly the same result found directly in paragraph 2.6. To
immediately verify this assertion set
in (3.13) and compare it with
(2.28a).
Besides the simplicity of the procedure, the Rosenstark method, gives
precise information on the ideal behavior of the common Z amplifier through
the asymptotic gain and illuminates how an increase in the loop-gain,
T,
moves the final transfer function close to its ideal value
3.4 THE CHOMA METHOD
Like the Rosenstark method, the one proposed by Choma starts from the
signal flow representation expressed by relationship (3.6), but adopts as
reference the relation in (3.
1
a), according to
In this case, only the denominator is expressed in terms of loop gain,
T.
The
whole function is multiplied for weight which represents the Direct
Transmission Term, and the numerator now depends on a novel
parameter termed the
null return ratio,
Thus the exact input-output
transfer function of the feedback amplifier is given by [C91]
where, of course, (3.8a) and (3.8b) hold, and
