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THS3095: Use in a PI-regulator to drive a Mosfet for current regulation

Part Number: THS3095
Other Parts Discussed in Thread: LM7171, , THS3491



I am working on a PI regulation design, where I currently use the LM7171 OpAMP to regulate the gate of a Mosfet to control the current through the Mosfet, with a supply of +-15V and a RC feedback loop.

Currently, I am using the LM7171 with several mosfets at the output. Hence the OPAMP needs to drive quite some capacity. Thus, at big regulation jumps at the input the OpAMP goes into current limitation and gets quite hot. To speed up the regulation and improve the thermal situation, I am looking for an OpAMP with higher output current capability and better thermal properties (power pad), like the THS3095.

Would you in general recommend to use the THS3095 for a fast PI regulation circuit or any other OpAMP from you portfolio?

In case I would replace the LM7171 with a THS3095 I face another challenge. The max differential input voltage for the THS3095 is 4V (LM7171 has 10V), but in my current layout I have a max input range of 10V. Can you tell me whether there is any internal protection in case of differential voltages >4V or make a suggestion for an efficient protection circuit, which does not influence the PI regulation too much.


In another question from a user I read you do recommend not to use the THS3095 in saturation, because of slow recovery. Do you offer another OpAMP, which is suitable for a fast PI-regulation and has a fast recovery?


Thanks and best regards


  • Morning Matias, 

    You have covered quite a lot here. Without the schematic hard to get too definitive on a solutions but - 

    1. Moving to the THS3095 you have gone to current feedback which is quite different. 

    2. Normally you do not want to go into overdrive on those as their recovery is not that well specified or modelled. 

    3. directly driving a cap load on these is always a stability risk

    4. But if you must, look at the THS3491 as the highest Io, slew rate, and speed CFA. Also its model is the most recent and complete. 

    Perhaps work up an initial sim with either the THS3095 or THS3491 to take this further? A TINA file always moves things along much faster.