Cirrus Logic AN300 REV1 - Manual (Page 9)

AN300REV1 9
AN300
Figure 12. Open Loop Gain Comparison
If an operational amplifier with only 120 dB of open loop gain is configured for a forward gain of 400X (52 dB). This
leaves only 68 dB of loop gain. A loop gain 68 dB is a factor of about 2500. Therefore, this amplifier set for a closed
loop gain of 52 dB, would be able to reduce open loop linearity error by a factor of 2500. This factor is a billion
times less (that is 1,000,000,000 times less) than what the CS3001 can achieve in the same configuration.
-20
0
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Frequency (Hz)
0.1 10 1k 100k 10M 0.01 1 100 10k 1M
Typical Op Amp
CS3001
52
Gain = 52 (400X)
Gain = 120 - 52 = 68
Loop Gain = 300 - 52 = 248
AOL = Open Loop Gain.
200
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300
ACL