Op Amp Voltage Follower – Single Supply

Op amp wired as a voltage follower output the same voltage that is at their input.

Operational amplifier voltage follower using LM358 op amp learning electronics lesson 0022
Operational amplifier voltage follower using LM358 op amp learning electronics lesson 0022

There are many ways to generate a signal voltage that is less than the supply voltage. However, that signal voltage will probably not be able to power a desired load. Pulling current from it will drop the voltage.

An operational amplifier can look at that signal voltage, and output that same voltage as the signal. Usually being able to provide a lot more current.

  • Lower inverting input (-) voltage than non inverting input (+) voltage = output voltage goes up
  • Higher – input voltage than + input voltage = output voltage goes down
  • Connecting the output directly to – (negative feedback) means that the output voltage will move towards the + input V until they are the same voltage.
  • The output will provide the current needed to power a load while staying at the + voltage.  Only able to do so if it stays within it’s output power limits of course.

The LM358 is a well known single supply op amp.

Video:

Single supply op amp:

Single supply output voltage can drop all the way to the negative supple voltage when powered by a dual supply, or to 0V ground when powered by a single supply power source. The output however will probably be at least a volt or 2 shy of outputting the full positive voltage of the supply powering it.

Always consult the datasheet for the part number of the integrated circuit you are using. That’s he best way to learn it’s limitations.

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