- Thu Oct 03, 2013 8:44 am
#164115
Hello,
I am so discouraged with these op amps...
In spite of all the equations I know, I have been trying for days to get an op amp to do the following ramp:
(V1) Input: must be a constant 5Vdc!
(V2) Input: 9 to 12Vdc
(Vout) Output: 3.5 to 6.3Vdc
ra = 10K ohms
With all desperation, I have been trying to calculate resistors r1, r2 and rf and it seems that I am not able to do it.
Internet articles only show equations on how to calculate Vout, but in reality, many times, we know Vin and Vout and need to solve for the *resistors*. And often we need the op amp to do ramps too. I don't get why there is no such simplified examples around the Internet or tutorials.
If someone knows the maths on how to calculate this, please get back. I am not looking for a quick answer (or circuit) calculated by some op amp calculator or LTSpice or other! I am looking for the mathematical breakdown to this solution! :neutral:
Thanks!
I am so discouraged with these op amps...
In spite of all the equations I know, I have been trying for days to get an op amp to do the following ramp:
(V1) Input: must be a constant 5Vdc!
(V2) Input: 9 to 12Vdc
(Vout) Output: 3.5 to 6.3Vdc
ra = 10K ohms
With all desperation, I have been trying to calculate resistors r1, r2 and rf and it seems that I am not able to do it.
Internet articles only show equations on how to calculate Vout, but in reality, many times, we know Vin and Vout and need to solve for the *resistors*. And often we need the op amp to do ramps too. I don't get why there is no such simplified examples around the Internet or tutorials.
If someone knows the maths on how to calculate this, please get back. I am not looking for a quick answer (or circuit) calculated by some op amp calculator or LTSpice or other! I am looking for the mathematical breakdown to this solution! :neutral:
Thanks!
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