LM2904: Frequency Response

May

Part Number: LM2904

Hi,

Customer want to know more about the op-amps, please see details below.

"For all of OPAMPs, the Gain-Frequency characteristics have -20dB/Decade. I want to know the reason why limited -20dB/Decade. Seems some R and C network inside. Can I have some explanation for above?"

Thank you in advance.

Regards,
Maynard

over 3 years ago

0 Ron Michallick over 3 years ago

TI__Guru**** 166026 points

Hello Maynard,

A more complete answer is here: https://training.ti.com/ti-precision-labs-op-amps-bandwidth-bode-plots-cutoff-frequency?context=1139747-1139745-14685-1138800-13124

The short answer is that the capacitance that can't be avoided (in an op amp) will create a lot phase lag becoming a stability problem starting at some frequency. Op amps have a lot of DC gain. Op amps have to get rid of that gain before that problematic frequency. The most simple solution is a dominant single pole (R C low pass) which has a -20dB/decade roll off and 90 degrees phase lag.

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LM2904: Frequency Response