I read a paper about application of circuits kind of similar to this one a few months ago. I try to find and post it here. Meanwhile I look for the article can you tell me the correct definition of gain bandwidth product. I checked definition of Gain Bandwidth Product in op amp design. but they were slightly different from each other.
Hi,
The gain bandwidth product GBP is a very simple concept. An amplifier has limitations, and the GBP is one that involves the gain you can get from the amp vs the frequency you intend to use it at.
As the frequency rises, the amplifier gain decreases naturally due to internal structure. The gain goes down inversely proportional to frequency. So if you get a gain of 10 at 100kHz, then you get a gain of 100 at 10kHz, and a gain of 1000 at 1kHz. Going up, at 1MHz you only get a gain of 1.
This means you can look up the GBP of the op amp and divide by the frequency in order to get the maximum gain you can get at that frequency.
For example, for a GBP of 1000000 (one million) if we want to operate at 1Khz then we divide this by 1000, and we get 1000 as the result:
1000000/1000=1000
This means the max gain we can get is 1000
It should be carefully noted that this is the "max" gain that we can get, but there is another constraint called the slew rate that also limits the frequency we can use the op amp at without distortion. The slew rate limits the rate of rise of the output of the op amp, regardless what the gain is. The only way we can really get the max gain is if we keep the output level below a certain peak level.
We can talk more about this once you have had time to think about the GBP.
More examples for an op amp with a GBP of 1000000:
F=10, max gain=100000
F=20, max gain=50000
F=500kHz, max gain=2