I hope someone can help me. I'm not an electrical engineer by occupation. I have a need for a circuit that can do the following:
Provide a steady 8 V DC output at rest. Add to that output, the voltage seen on a potentiometer wiper (0 to 7.8 V). In other words:
From the research I've done so far, it seemed as though a couple of inverting op-amps would be the answer (the first an inverting summing op-amp so that the 8 V baseline supply input and the potentiometer input wouldn't interfere with each other, the second with a unity gain to simply invert the output of the first).
Is there an easier way to achieve it or is this the best approach?
I've tried breadboarding it with an LM324 and I'm not seeing the results I'm expecting, due possibly to my running the op-amp from a single 18 V DC supply instead of a +16/-16 V supply.
Thanks to everyone for taking the time to answer and explain. What a great community!
Apologies for the delay in responding. The nature of my work means I am away from mobile and internet access until I get home :(
I will try the suggested circuits, using the LM358 and a 24 V supply.
To follow up on some of the comments, here is the circuit I had tried breadboarding before. All resistors used were 1% metal foil. The variable 0-7.8 V input is the resultant voltage from a 10k linear potentiometer attached to a speed controller circuit.
I'll be sure to post my progress using the suggested circuits Thanks again for your time and expertise to help me with this!