How can i make an amp op response faster??

[bubulindo]

How can i make an amp op response faster??


Hi, i'm using an amp-op to measure a resistance of 120GOhm, yes that's correct, and my amp-op takes about 2,5 seconds to settle the signal.

How can i make it faster?


best regards, Carlos

Best regards, Carlos Cardoso

 

[IRstuff]

No, your 120GOhm resistor is taking 2.5 seconds to settle, as you should have expected.

Since this looks to be about 7 pF of node capacitance, I suggest that you look to see about minimizing the parasitic capacitance, e.g.:

Are you using a FET input op-amp?

Are you minimizing trace lengths and widths?

Are you using driven shields?

TTFN

 

[Heydave]

You could possibly use a flying capacitor scheme to precharge the circuit based on the rate of change. Is this a chopper stabilized op amp? PCB surface leakages and cable capacitance can be reduced through driven shields and guard traces but the capacitance of the test subject cannot be nulled without some precharging. What is the approximate capacitance of the resistance you are measuring?

 

[bubulindo]

Has it is expected, i'm using the state of the art in op amps, I used OPA128, but his slew rate was too small, and the settling time was about 4,5 seconds. So i've switched to OPA627 that has a bigger slew rate but higher leakage currents. Yet it takes about 2,5 seconds.

Thanks for your tips

Best regards, Carlos Cardoso