Other Parts Discussed in Thread: LF353, , OPA4172
Tool/software:
Hi,
We have a legacy design with a differential mode op-amp that uses LF353. We have high CM noise input to the differential circuit and we only care about DC input…
Hi Liam,
Yes, the circuit as you have modified appears to work in a linear fashion now. I don't have any more ideas why the OPA1652 input is clamping at Vin > 0.9 V input.
Do you have type of precision op amp you can substitute for the OPA1652,…
Hi Thomas,
they did have a 1k resistor on the output but i removed it as it was causing the overheating. (i didnt include it in the diagram because i had removed it from the board already) I only mentioned it because we were discussing the posibility…
Hi Liam,
The OPA1652 op amps in your application circuit do not have any significant resistive loads on the output so they shouldn't be consuming much current beyond the quiescent current. They only draw about 2 mA and shouldn't be getting hot to the…
Hi Thomas,
So today i tried my other board...i removed the cap from the output of opamp a and the resistor from the output of opamp b . I also removed the feedback from 2 out of the three instances of the circuit on this new board. I then powered and…
Hi Thomas,
Thanks again for the help. Yesterday i removed the feedback from opamp B to the inverting input of opamp A and the DAC was able to reach 5v so im now sure that it is the feedback between the opamps that is causing the issue. The board i am…
Hi Liam,
Thank you for providing the DAC information. I don't find any reason why it should have an issue directly driving the OPA1652 input in a properly functioning circuit.
Our op amp products are fully analyzed and then tested for latch-up behavior…
Hi Thomas,
Yes this was what was making me think the op amp is damaged or in latchup. the DAC im using is a MAX5216. i have tried it with the outpit disconnected from the opamp input and i can see the output go from 0-5v as i would expect. its only with…
Hi Liam,
The OPA1652 input following the DAC should not load its output. It has an extremely high input impedance. What is the DAC part number that you are using in the circuit? Is it truly a voltage output DAC?
Regards, Thomas
Precision Amplifiers Applications…
Hi Thomas,
thanks for getting back to me. The supply is +-15v. I have removed the 100nF cap from the output of the first opamp and it doesnt seem to have made much difference. The opamps arent getting hot any more after i removed a 1k pull down resistor…
Hi Liam,
What supply voltages are you applying to the OPA1652 supply pins, and the using to power the solenoid? This circuit may have stability problems due to the design. The OPA1652 is very likely to become unstable with a 100 nF capacitor, and the…