Op Amp Voltage Follower – Single Supply

Op amps that are 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 because 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 than most signal voltages.

  • 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 as long as you stay within it’s limits.

The LM358 is a well known single supply op amp.


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Video:

Single supply op amp:

IC output voltage range illustrated for dual split supply single and rail to rail diagram by electronzap electronzapdotcom
IC output voltage range illustrated for dual split supply single and rail to rail diagram by electronzap electronzapdotcom

Single supply output voltage can drop all the way to the negative supply voltage.

The negative supply voltage is ground for a single supply power source, and is a negative voltage in relationship to ground for a dual voltage supply.

Single supply integrated circuits tend to have an output that falls at least a volt short of the positive supply.

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

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