# Predicting AC open-loop gain for an internally compensated op-amp

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1. Sep 26, 2016

1. The problem statement, all variables and given/known data
An internally compensated op amp has a DC open-loop gain of 1,000,000 (V/V) and an ac open-loop gain of 40dB at 10kHz. Provide the expected gain in dB at 1kHz...

2. Relevant equations

3. The attempt at a solution
Beyond the break-point, the gain goes down as frequency goes up. So I just picked the value larger than 40dB (since the frequency decreased).

Last edited by a moderator: Sep 27, 2016
2. Sep 27, 2016

### Staff: Mentor

How many poles does an internally compensated opamp typically have, and where located? So what would you expect the rolloff to be in the 10kHz to 1kHz region?

3. Sep 27, 2016

What? Is there another word for poles or rolloff? I don't know what these mean.
Is my intuitive answer usually how this problem would be answered?

4. Sep 27, 2016

### Staff: Mentor

What class are you in? What textbook are you using? What have you found when you use the very helpful Internet to search for information on Dominant Pole Compensation for Opamps?

5. Sep 28, 2016

302 Analog electronics
https://www.uwplatt.edu/files/colla... ENGINEERING TECHNICAL ELECTIVES.4.14-2_0.pdf

Microelectronics 4th edition by Neamen

Thank you for giving me a precise phase to search and learn about:
https://en.wikipedia.org/wiki/Operational_amplifier#Frequency_compensation
half-power frequency = 3dB down frequency vs the unity gain frequency...(Note to self - Lab Design project #1 III. Measurements, Amplifier gain)
http://www.ti.com/lit/an/sloa020a/sloa020a.pdf#page=19
http://web.mit.edu/klund/www/papers/ACC04_opcomp.pdf

I have to go, but I will come back and read more about this...

6. Sep 28, 2016

### Staff: Mentor

You are heading in the right direction, but just saying the gain is "greater" is not an answer to the question
Answering those questions will give you the quantitative answer...

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