0
\$\begingroup\$

This is my non inverting OP AMP based amplifier for one of my measuring circuit. enter image description here

I have 2 queries about this circuit:

  1. With maximum input voltage of 5 V, I'm getting only 3.7 V only. (I know the concept of Rail to Rail , but with this circuit how can I stretch it to maximum possible output)
  2. VR2 pot is for offset nulling purpose is not showing any effect on output voltage.

Please suggest.

\$\endgroup\$
5
  • 1
    \$\begingroup\$ The datasheet for OP07 only allows a minimum supply voltage of 6 V (not 5), and only promises an output swing within 3 V of the rail (not the 1.3 V that the model achieved). You might get slightly better by increasing R13 and R14, but really if you want rail-to-rail output you just need to pick a different op-amp. \$\endgroup\$
    – The Photon
    Commented Aug 14, 2023 at 4:50
  • 1
    \$\begingroup\$ You're already getting the maximum possible output. The OP07 is not even close to a rail-to-rail op amp, and isn't really suitable for the task you're using it for here. \$\endgroup\$
    – Hearth
    Commented Aug 14, 2023 at 4:50
  • \$\begingroup\$ The OP07 is very old. Use a newer opamp design. \$\endgroup\$
    – Audioguru
    Commented Aug 14, 2023 at 14:28
  • \$\begingroup\$ @Audioguru do you know any cheaper Op Amp with compitability with OP07? \$\endgroup\$ Commented Aug 16, 2023 at 5:20
  • \$\begingroup\$ Cheap usually means poor or no specs. \$\endgroup\$
    – Audioguru
    Commented Aug 26, 2023 at 1:37

1 Answer 1

2
\$\begingroup\$

As in the comments the op-07xx is not suited to output values close to the + or - supply rails. If you want an accurate output with a 0-5V input consider using bipolar supplies of +-12V or greater. (You could also select a true rail to rail op-amp part.)

The offset potentiometer will only adjust a few millivolts, but if you are already over the maximum output voltage range you won't see any adjustment. Even if within the normal operating range the small gain of your design may make the null adjustment hardly noticeable.

\$\endgroup\$
1
  • \$\begingroup\$ Thanks for suggestion sir. \$\endgroup\$ Commented Aug 14, 2023 at 7:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.