OP4177 opamp is not working as voltage limiter.

Hi!

I am facing some issues with OP4177 (precision amplifier)  in a voltage limiting application. Earlier in the design LM-148 ( quad uA741) was used and there was absolutely no issue. In the same configuration OP4177 gives horrible results with absolutely no clue.

Am attaching the circuit and practical results for reference.

Please advice.

Regards

Ruchi

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  • Ruchi,

      AR4A, etc. are connected in such a way where under certain conditions, the diode is reverse biased and there is no feedback.  A lot of op amps don't like this.  The OP4177 is a precision op amp with protection diodes and resistors between the inputs to protect the diff pair.  See OP177 data sheet for a similar schematic.  In addition, Some quads have one, or two or four bias networks.  I don't know about the OP4177, but if it has one bias network, if one section is overloaded, it can affect the other three.

    The LM148 is a commodity, non precision op amp.  If it works in your system, why do you want to change it?

    Harry


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