oscarcot
Junior Member level 1
Hello,
I'm designing an amplifier for a fixed gain of 60dB and 10kHz bandwidth. (Just for reference, it is a Fully Differential Difference Amplifier, using XH035 CMOS-technology). The DC open-loop gain is 85dB. I read from some references that the open-loop gain needs to be at least 20dB above the closed-loop gain, which I think is more or less satisfied by my specs.
1. Now the question: do I need a gain of 80dB at 10kHz?
'cos there's an issue: if I do so, I'll end-up with a bandwidth of 100kHz when I use the 60dB closed-loop gain. That will bring more noise into the system which sooner or later would have to be filtered out.
This is a medical research application, so we're in fact more concerned about the noise performance, signal shapes and relative amplitudes rather than the absolute voltages.
2. If I implement a 10kHz low-pass using such amplifier, won't I still have some kind of gain-error?, I mean, precisely 3.01dB gain-error?
3. What is the relevance of the gain error besides knowing "I know that my gain is not accurate from 6 to 10kHz"? I would rather overcompensate the amplifier and restrict the bandwidth to 10kHz.
Can somebody help?
Cheers,
Oscar
I'm designing an amplifier for a fixed gain of 60dB and 10kHz bandwidth. (Just for reference, it is a Fully Differential Difference Amplifier, using XH035 CMOS-technology). The DC open-loop gain is 85dB. I read from some references that the open-loop gain needs to be at least 20dB above the closed-loop gain, which I think is more or less satisfied by my specs.
1. Now the question: do I need a gain of 80dB at 10kHz?
'cos there's an issue: if I do so, I'll end-up with a bandwidth of 100kHz when I use the 60dB closed-loop gain. That will bring more noise into the system which sooner or later would have to be filtered out.
This is a medical research application, so we're in fact more concerned about the noise performance, signal shapes and relative amplitudes rather than the absolute voltages.
2. If I implement a 10kHz low-pass using such amplifier, won't I still have some kind of gain-error?, I mean, precisely 3.01dB gain-error?
3. What is the relevance of the gain error besides knowing "I know that my gain is not accurate from 6 to 10kHz"? I would rather overcompensate the amplifier and restrict the bandwidth to 10kHz.
Can somebody help?
Cheers,
Oscar