CS3011
CS3012
Vin
Cin
50 pF
50 pF
Vo
Cin
R2
C2
R1
Choose C2 so that R2 • C2 ≥ R1 • Cin
?
Figure 16. Non-Inverting Gain Configuration with Compensation
The feedback capacitor C2 is required for closed-
loop gains greater than 50 V/V. The capacitor intro-
duces a pole and a zero in th e loop gain transfer
function.
s
– 1 + ----
z1
----------------------
T =
Aol
s
p1
1 + ----
1
1
------------------------------------ ------------------------
P1
=
≅
for
R2 » R1
||
2π(R1 R2)C2 2π(R1C2)
R2
A = -----
R1
1
Z1 = -----------------------------------
where
2π(A × R1)C2
1
Z1 = ------------------------
2π(R2)C2
This indicates that the separation of the pole and
the zero is governed by the closed loop gain. It is
required that th e ze ro falls o n the steep slo pe
(–100 dB/decade) of the loop ga in plot so that
there is some gain higher than 0 dB (typically 20
dB) at the ha nd-over frequency (the frequency at
which the slope changes from – 100 dB/decade to
–20 dB/decade).
DS597F6
11
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