1
\$\begingroup\$

I want to make a circuit using opamps and passive components where the input is a pulse train and can be with a frequency between 100kHz upto 3MHz and the duty cycle can be 100% or down to 1ns ON time. I want to average such an input and set a threshold like 0.5V. And if the average is less than 0.5V the final output will be logic zero otherwise logic 5V.

I tried the following approach myself using an RC integrator and a buffer:

enter image description here

How can this circuit be improved regarding the definite input? Response time I need is less anything than 10ms.

\$\endgroup\$
1
  • 1
    \$\begingroup\$ if you need to output a true/false signal based on a threshold voltage, think about a comparator instead of the opamp buffer. That means: remove the negative feedback and apply a 0.5 V DC signal to the inverting input. The output will be your digital signal. \$\endgroup\$
    – tobalt
    May 10, 2021 at 12:05

1 Answer 1

1
\$\begingroup\$

Make a comparator instead of the voltage buffer. The R2 is optional but makes the output slightly hysteretic around 0.5 V input. Be sure to select an opamp/comparator part which has a common mode input range down to within 0.5 V of the negative supply and ideally ral-to-rail output, to provide a full swing digital signal.

enter image description here

\$\endgroup\$

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.