Other Parts Discussed in Thread: THS3491, , OPA548
Hello!
I always thanks for your great supports.
Back in the last thread, I solved problem to reduce the cable and improve Rf 30 to 800ohm. (Thanks Kai )
But unfortunately, I can't use THS3491 in my circuit. Based on my application, I have to use 30ohm as a Rf.
and I have to use Cf to cut-off high frequency noise.
So I bought some THS4631 (Voltage Feedback Amp,) and now I found out it works I expected. (I can use 30ohm and also Cf)
But there is a problem now and I'd like to ask you the advices.
The current range we'd like to get is very big. (0~2A)
and Frequency range is also very wide (20~1MHz with no delay (no phase delay at 1MHz))
So I tried to use THS3491 (which has 420mA output current) for my application,
But now I realized that Ths3491 can't use small Rf (like 30ohm) and also can't use Cf.
To use 3491, I tried to use big resistor inner roop, (800ohm) (please refer the circuit in previous thread.) It works, but when the load goes to high or the cable goes to long or the input of negative feedback is open,
The output voltage starts to ringing. I think inner roop Resistor makes system quite unstable. I don't know why.
So I think the best way now is use 20 parallel of THS4631 (or other Amps. please recommend)
like below.
Is it possible?
I checked that when I 2-parallel of 4631, the output voltage of each Amp. has different DC offset voltage.
But it was small (500mV↓). and the sum of them was zero. So I think It can be ignored.
But I worried when the parallel OP-amp. are more, one of them has very big offset voltage.
anyway, I think it looks weird too.
But I don't have other idea to meet my system requirement.
I want to ask you that, is it possible? and Is there an any good idea to get 0~2A current without any phase delay from 0~1MHz?
I can't add any parts in negative input line.
Actually, Money is no object in this project.
Thanks.