Design an Op Amp circuit to meet specs

Discussion in 'Homework Help' started by Robert Murch, Mar 7, 2016.

1. Robert Murch Thread Starter New Member

Nov 2, 2015
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So for a class activity in school we are to design an Op Amp circuit (any number of 741 Op Amp's) that must have the following characteristics:

DC voltage gain (Vout/Vin) of 40 dB +- 1 dB
DC phase shift of 180 degrees (input to output)
Gain to be achieved with a Thevenin equivalent resistance of 10k Ohm's driving the amplifier
Gain to be achieved with a 10k Ohm load
3dB Bandwidth >= 40 kHz
Bipolar supplies of +-15V

So me and my partner have completed the project but we had to use two Op Amp's to do it. What I was wondering is could it be done with one and if so could you tell me what kind of configuration would be required.

2. WBahn Moderator

Mar 31, 2012
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What is the gain-bandwidth product of a 741 op amp?

What is the gain-bandwidth product of your amplifier?

3. Robert Murch Thread Starter New Member

Nov 2, 2015
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Ah I see now the GBP of the 741 is just too small 10 kHz. So, I am assuming I could complete this with only one Op Amp if i was not using 741's?

4. WBahn Moderator

Mar 31, 2012
18,088
4,917
I think the GBP for the 741 is generally given as being about 1 MHz, not 10 kHz. But with a voltage gain of 40 dB (or 100) and a bandwidth of 40 kHz, you would need a GBP of about 4 MHz.

There are numerous op amps that satisfy that requirement. Though there are other performance parameters that would have to be considered as well.

5. Robert Murch Thread Starter New Member

Nov 2, 2015
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Okay here's my next question in our circuit we utilized a few capacitors and some resistors along with two Op Amp's. I was told by another student that it could be done with one inverting Op Amp and one non-inverting Op Amp a few resistors and no energy storage element, is that possible? I was under the impression that the energy storage elements are what's creating the pols and zeros (sorry just starting learning about network functions).

6. WBahn Moderator

Mar 31, 2012
18,088
4,917
But do you need any poles or zeros?

Remember, the bandwidth spec is a minimum.