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Original question:

need information

OPA602: take an output voltage from an optical sensor and convert that signal to an output signal between 0-1VDC

Marvin Cantos
Expert 5695 points
Part Number: OPA602
Other Parts Discussed in Thread: LM6142, TL071

Hi Team, 

Good day. I am posting this inquiry on behalf of the customer.

"I am looking for a replacement for OPA602AP.

I would also only like through-hole parts, no soldering is required

I am trying to take an output voltage from an optical sensor and convert that signal to an output signal between 0-1VDC

The min and max voltage of the Optical sensor is between 0.3VDC and 2.8VDC

the main inquiry is a replacement device for OPA602AP

the other information is to give context to the project I am working on and the goal I am trying to achieve

I simulated the circuit using a product that is obsolete and therefore needs something that will do the same thing."

Please help to advise. Thank you for extending your support.

Kind regards, 

Marvin

  • 0
    Guru 296910 points

    This simulation is not realistic; the OPA602 does not have rail-to-rail inputs and cannot handle signals near the supplies.

    The LM6142 has rail-to-rail inputs and outputs, and somwhat similar characteristics. Other replacements are likely to be possible, but we need to know what frequency, offset error, noise, and power supplies are required.

  • 0
    Guru 140200 points

    Hi Marvin,

    I don't understand the supply voltages of OPA602 in the schematic. Is it +10V single supply? Or is it a bipolar supply voltage of +/-10V? Or a bipolar supply voltage of +/-5V?

    I think the TL071BCP could eventually be used as a direct drop-in replacement. Or a similar JFET-OPamp with a somewhat lower input offset voltage?

    Kai

  • 0
    TI__Guru 61771 points

    Hi Marvin, 

    Both suggested op amps may work from Clemens and Kai. If you are looking for low Ib op amp replacement, TL07x may meet the requirements. Otherwise, LM6142 will work. 

    https://www.ti.com/lit/ds/symlink/tl071h.pdf?ts=1678720283284&ref_url=https%253A%252F%252Fwww.google.com%252F

    Can you tell us what you are trying to do? OPA602 and TL071 JFET op amps have higher Vcm ranges, so the input voltage of 0-2.8Vdc to 0-1Vdc may not be the best option. Here are couple issues that I can see. 

    1. The input Vcm may create issues for the op amps, even with OPA602 (violate the common mode input voltage, unless certain dual supply voltage rails are used.). 

    2.  You may loose accuracy or create large unwanted error by doing the conversion. 

    3. Vos voltage may not meet the accuracy requirements per the application. 

    Please let us know the design requirements or application; perhaps we can come up with a better solution. 

    Best,

    Raymond