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Voltage Follower Calculator

Work out voltage follower instantly with clear inputs, formula shown and shareable results.

About Voltage Follower Calculator

A voltage follower has unity gain with an error of just 1/(1 + A), so with an open-loop gain of 100,000 the error is 10 parts per million. Its value is impedance transformation: a high-impedance source driving a low-impedance load loses most of its signal without a buffer.

Formula

Voltage follower

Vout = Vin x A / (1 + A); without a buffer Vout = Vin x ZL / (ZS + ZL)

Worked example

With the default values below, Voltage Follower Calculator returns Output voltage of 1.649984. Change any input above and every figure here is recalculated in your browser.

Inputs used

Input voltage
1.65 V
Source impedance
100,000 Ω
Load impedance
600 Ω
Op-amp open-loop gain
100,000 x

Results

Output voltage
1.649984 V
Gain error
0.00100% %
Signal without the buffer
0.00984 V
Improvement factor
167.67 x

Step by step

  1. 1Values used
  2. 2Voltage follower
  3. 3Output voltage= 1.649984 V
  4. 4Gain error= 0.00100 %
  5. 5Signal without the buffer= 0.00984 V
  6. 6Improvement factor= 167.67 x

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 6 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

Why is a follower useful if the gain is one?

Because it converts a weak high-impedance signal into a low-impedance one that can drive a real load without attenuation.

Are all op-amps stable at unity gain?

No. Decompensated types are only stable above a minimum gain, so check the datasheet before using one as a follower.

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