... 320mv . . . 500mv ...

↓ ? what OpAmp ↓ /// is the supply ±15V or other /// is there any load from OpAmp OUTP to anywhere (other than the feedback resistor) ?

↑ about offset trim ↑ https://www.maximintegrated.com/en/design/technical-documents/app-notes/8/803.html

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items to check ::

is how you get your +V2 (+5V) --and-- does it stay that during pot adjust
. . .
note: the skin conductance is at the range of your biasing resistors

 

Guys, I got it to work like a charm. I just tweaked the 150k and got down from 1v to 0v , exactly what I needed
Also fed a waveform into it and got exactly the output I was looking for.
@ci139 it was 4558 op-amp
Everything is all good,
thank you again, if I have any other issues, I will revisit this forum for advice.
Have a great day!!

 

just FYI if anyone's interested ::

• TL072 ti variant --- Is=1.4mA Vs=(±3.6)..±18V SR=13V/µs GBW=3MHz Vio=3mV Iio=5pA Ib=65pA 18nV/√Hz(1kHz)
• TL3472 ti variant --- Is=3.5mA Vs=(±2)..±18V SR=13V/µs GBW=4MHz Vio=1mV Iio=6nA Ib=100nA 49nV/√Hz(1kHz)
i likely got NJM4560 -- Is=4.3mA Vs=(±4)..±18V SR=4V/µs GBW=10MHz Vio=0.5mV Iio=5nA Ib=40nA 10nV/√Hz(1kHz) somwhere
• RC4558 ti variant- Is=2.5mA Vs=(±3.6)..±18V SR=1.7V/µs GBW=3MHz Vio=0.5mV Iio=5nA Ib=150nA 8nV/√Hz(1kHz)
• µA741 ti variant ----- Is=1.7mA Vs=(±2)..±18V SR=0.5V/µs GBW=1MHz Vio=1mV Iio=20nA Ib=80nA 8nV/√Hz(1kHz)

the RC4558 is said to be a 2-ch µA741 Op Amp
they show equivalent circuit for the RC4558 that has it's Output stg. similar to that on TL071 d/s (also the input one)
the TL3472 is said to be (somewhat) a bi-polar input (= lower operating voltage) substitute for TL07x/8x
so the RC4558 appears to be a lower slew rate bi-polar (input) substitute for TL072/82 (with lower voltage noise)

basically the RC4558 said to be "a matched pair" of opamps -- so i guess the offset zero error is not too great also

RC4558's offset zero error for the Spice model →

← interestingly the TL3472 higher slew rate does not show out (perhaps because it's lower input sensitivity)