What is the expected gain of a unity-gain buffer amplifier?

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From the video: The gain expression for the non-inverting amplifier is,

$v_o = v_{in}$

The gain is $1$.

Open a blank schematic.

Design and simulate a unity-gain buffer amplifier with a gain of $1$.

  • Drive the unity-gain buffer with a sine wave voltage source.

  • Add a voltage probe on the output port.

  • Click on TRAN to run a transient simulation.

Does the simulation match your gain calculation?

Add a voltage probe to $v_{in}$ and simulate again.

Notice how the output and input voltages overlap.

Change the value of the input voltage and run another TRAN.

Verify the buffer amplifier does what you expect.

Click the download icon.
Open the resulting data.csv file in Excel or Matlab or any text editor.

Notice that $v_o$ and $v_{in}$ are the same. When we model an ideal opamp the virtual ground is perfect, $v_o = v_{in}$. In the real world there will be a very slight difference due to the offset voltage of a real opamp. You find the offset voltage listed on the opamp’s data sheet.

unity-gain buffer amplifier

Simulation model of a unity-gain buffer amplifier.