CS3001
CS3002
Open Loop Gain and Stability
Compensation
The CS3001 and CS3002 achieve ultra-high open
loop gain.
illustrates the amplifier in a
non-inverting gain configuration. The open loop
gain and phase plots indicate that the amplifier is
stable for closed-loop gains less than 50 V/V. For a
gain of 50, the phase margin is between 40° and 60°
depending upon the loading conditions. As shown
in
the op amp has an input ca-
pacitance at the + and – signal inputs of typically
3.2
50 pF. This capacitance adds an additional pole in
the loop gain transfer function at a frequency of
f = 1/(2πR*C
in
) where R is the parallel combina-
tion of R1 and R2 (R1
||
R2).
A higher value for R
produces a pole at a lower frequency, thus reducing
the phase margin. R1 is recommended to be less
than or equal to 100 ohms, which results in a pole
at 30 MHz or higher. If a higher value of R1 is de-
sired, a compensation capacitor (C2) should be
added in parallel with R2. C2 should be chosen
such that R2*C2
≥
R1*C
in
.
R
S
V in
Vo
R2
R1
Figure 10. Non-Inverting Gain Configuration
8
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