The frequency changes from the AD9833 DDS chip but it has a 0.6V pk to pk and I need it to be 1V to 10V pk to pk this is my circuit so far the goal is to have an adjustable gain please any adjustments will be welcome.

enter image description here

  • \$\begingroup\$ Is the same circuit as the other question Adding programmable amplitude control to an AD9833-based function generator? \$\endgroup\$ Commented Mar 24 at 22:57
  • \$\begingroup\$ that was 5V pk to pk the concept is similar \$\endgroup\$
    – zug
    Commented Mar 24 at 22:58
  • \$\begingroup\$ the title does not describe the question ... please correct it \$\endgroup\$
    – jsotola
    Commented Mar 24 at 23:01
  • 1
    \$\begingroup\$ @zug - You can't have this new question and change your previous question to be asking the same thing. That causes duplication of effort. || I will reverse your previous question to the state when it was answered. Please consider whether you can áccept the answer you got to that question. || In any case, if that question is no longer relevant to you then please edit that question, to make it clear that you don't need more help there. \$\endgroup\$
    – SamGibson
    Commented Mar 24 at 23:22
  • 1
    \$\begingroup\$ @ChesterGillon - Hi, FYI I have reverted that previous question back to the state when it was answered, to prevent it becoming a "chameleon question". This question is now a different circuit to that previous one. \$\endgroup\$
    – SamGibson
    Commented Mar 24 at 23:28

1 Answer 1


You have an inverting amplifier in your design, with R16 = 3.9k . To get a gain above 1 you will need the feedback (optoresistor) value bigger than 3.9k. However, if you check the datasheet for NSL-32SR3, you will find out that even at 0.1mA of input current the photoresistor has the value of about 2k, and no manufacturing data below that are provided, enter image description here

I would expect that if you reduce R16 to 100R and manage to control the LED current from 2mA down to 0.1mA, you will see some amplification.

Also note that you will need somewhat higher supply voltage to get 10V amplitudes out of it. The standard voltage is usually +-15V, not 10.


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.