/diy/ - Do It Yourself

>>2498229
>i will just follow their values for now
Those are values for the internal equivalent resistors of the INA217. If you're using the NE5532, the datasheet says in relation to a differential amplifier circuit:
>Because the transfer function of VOUT–
is heavily reliant on resistors (R1, R2, R3, and R4), use resistors with low tolerances to maximize performance and minimize error.
>This design used resistors with resistance values of 36 kΩ with tolerances measured to be within 2%.
>But, if the noise of the system is a key parameter, the user can select smaller resistance values (6 kΩ or lower) to keep the overall system noise low.
>This ensures that the noise from the resistors is lower than the amplifier noise.
So it would actually be a good idea to use low resistances like that, my mistake. With minimal voltage slew it's probably no big deal in terms of heat.

The NE5532 has a unity-gain-bandwidth of 10MHz, so at 20kHz it will have a gain of 54dB [20*log(10M/20k)], so yeah you couldn't get the full 60dB for the whole audio window even if you tried. I wouldn't trust it to behave well when set to that kind of gain, especially without using a filter to lower its high frequency gain below that. Not that I've really seen issues with running op-amps at the edge of their frequency range. Using a gain of ~31 for both the stages of an instrumentation amplifier would be my intention.
Say, 15k/1k for the first stage, and 33k/1k for the final stage, would give about 30dB each time, pic related. With 2.2nF caps across each 3.3k resistor, I think that will result in a decent frequency response, though I'd simulate it with an AC sweep to be sure though.

>>2498238
Doesn't a JFET only act as a source follower? I can't see how a JFET gives voltage gain, but I've never closely studied JFETs so who knows. In this instance, with more or less equal source and drain resistors, the voltage gain shouldn't be high either way, I think.