I have the TL071CP op-amp, and I am trying to make a simple DC voltage follower, however, I only get a couple hundred milivolts at the output. Usually 200-450mV. Any idea why?
simulate this circuit – Schematic created using CircuitLab
Why doesn’t the TL071CP op amp act as a voltage follower
operational-amplifiervoltage-regulator
Related Solutions
No, there is no way to make an inverting buffer with just an op-amp that does not depend on the resistor values. You can get resistors with very fine accuracy and stability (at an equally impressive price) or you can get networks with matched (in value and in temperature coefficient) where the absolute accuracy may not be so impressive but the ratio is tightly controlled.
There is a way to invert a signal without accurate resistors- the so-called flying capacitor method, but it's fairly complex and resistors are a better solution for most situations down to ppm level accuracy.
It can be used but for most op-amps the maximum current you would be able to drive from the output will be limited to less than 50mA. Op-amps are not miracle workers! On the other hand you can attach an NPN and PNP transistor in a push-pull configuration and get more current: -
(source: northwestern.edu)
Or, you could use an OPA541 - it is an op-amp and can supply up to 10 amps: -
I guess this one is a bit of a miracle worker!
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Best Answer
To expand on the comments a little: A TL071 is the wrong opamp for the configuration you're using, because you've exceeded the "Common-Mode Input Voltage Range" spec.
If you go to Table 6.3 on page 6 of the datasheet and look for the Vicr (Common-mode input voltage range) line you'll see that with a +15V/-15V supply (that's 30v from + to -), the minimum guaranteed input voltage range is +-11V. That's 4V away from each supply.
So, with your single 9V supply and the same rule applying, your input voltage must lie in the range of 4 to 5V in order for the opamp to behave properly. The 2.5V from your voltage divider is clearly out of range.
Even if you look at the more lenient data from the 'Typical' column, the range is -12 to +15 with +15/-15V supplies and this would lead to an input range of 3V to 9V with your single 9V supply. So your 2.5V input is still out of range.
Try to find an opamp which is intended to run from a single-supply (like an LM358) and you should see much better results.