I think you need to go back to first principles and review the proper opamp configurations and how to analyze them. For example if you replace all three resistors and connect an appropriate power supply you will have a voltage follower and by definition pin 2 and pin 4 will both have the same voltage and the difference between pin 1 and pin 2 will be very close to zero.
- It needs more attention. Pins 3 & 5 are the power connections, and the difference must be at least as large as the range of the input signal.
- Opamps start by computing the difference between the (+) or non-inverting input, and the (-) or inverting input.
- This difference is then multiplied by a large number on the order of 10^5 or 10^6
- In your configuration, the output at pin 4 will try to make the voltage at pin 2 equal to the voltage at pin 1 which is 24 volts. It may or may not be able to do this depending on things you have not shown on your schematic.
Why not use the Op Amp as a buffer and vary the + input voltage through a pot?
Looking at 40mThat configuration will not allow an output voltage less then the 24V to to the plus input, it can only amplify the voltage.
One way to adjust the output from 0V to 24V is to tie the op amp output directly to the minus input to make it a follower, and then use the pot wiper to output 0V to 24V at the plus input.
How much op amp output current do you need?
As the "track" of your digital pot has a resistance of 10K if you connect one end of the track to ground and the other end of the track to +24 volts via a 30K resistor you will have 6 volts across the ends of the track. (You have creates a simple potential divider.)
You then need to configure the OP amp to multiply it's 0 to +6 volt input by 4 to create a 0 to +24 volts output.
Depending on the op amp you use you may need its negative supply pin to be a few volts negative of ground.
Note I have never used digital pots so I am assuming they behave like a normal pot except fot the voltage limitations.
Hi Dave,Can I confirm as 100 and 10 ohms for gain of 1.1
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