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

In summary, an internally compensated opamp has a DC open-loop gain of 1,000,000 (V/V) and an ac open-loop gain of 40dB at 10kHz. The expected gain in dB at 1kHz is 40dB.
  • #1
adamaero
109
1

Homework Statement


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...

Homework Equations


Please help, I don't know what to use for an exact answer.

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).
 
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  • #2
adamaero said:

Homework Statement


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...

Homework Equations


Please help, I don't know what to use for an exact answer.

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).
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
berkeman said:
How many poles does an internally compensated opamp typically have, and where located?
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
adamaero said:
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?
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
302 Analog electronics
https://www.uwplatt.edu/files/collaborative-engineering/Documents/ELECTRICAL%20ENGINEERING%20TECHNICAL%20ELECTIVES.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
adamaero said:
ac open-loop gain of 40dB at 10kHz. Provide the expected gain in dB at 1kHz...
adamaero said:
So I just picked the value larger than 40dB
adamaero said:
Is my intuitive answer usually how this problem would be answered?
You are heading in the right direction, but just saying the gain is "greater" is not an answer to the question
berkeman said:
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?
Answering those questions will give you the quantitative answer... :smile:
 

1. What is an internally compensated op-amp?

An internally compensated op-amp is a type of operational amplifier that has built-in compensation circuitry to stabilize its open-loop gain. This allows for a more predictable and consistent performance, especially in high-frequency applications.

2. Why is it important to predict the AC open-loop gain of an internally compensated op-amp?

Predicting the AC open-loop gain of an internally compensated op-amp is important because it allows engineers to understand and optimize the performance of the op-amp in their circuit design. It can also help identify any potential stability issues that may arise.

3. What factors affect the AC open-loop gain of an internally compensated op-amp?

The AC open-loop gain of an internally compensated op-amp is affected by various factors such as the internal compensation circuitry, the frequency of the input signal, and the external feedback components used in the circuit.

4. How can the AC open-loop gain of an internally compensated op-amp be calculated?

The AC open-loop gain of an internally compensated op-amp can be calculated using its transfer function, which includes the internal compensation circuitry. This transfer function can be derived from the op-amp's circuit diagram and its small-signal model.

5. Are there any limitations to predicting the AC open-loop gain of an internally compensated op-amp?

Yes, there are some limitations to predicting the AC open-loop gain of an internally compensated op-amp. These include variations in component tolerances, temperature effects, and non-idealities in the op-amp's internal compensation circuitry. These factors can affect the accuracy of the predicted gain and should be taken into consideration in circuit design.

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