Voltage Follower Calculator Formula

Understand the math behind the voltage follower calculator. Each variable explained with a worked example.

Use the Voltage Follower Calculator

Formulas Used

Output Voltage

v_output = v_input

Load Current

load_current_ma = v_input / load_resistance_ohm * 1000

Without Buffer (loaded)

without_buffer_v = v_input * load_resistance_ohm / (source_impedance_kohm * 1000 + load_resistance_ohm)

Variables

VariableDescriptionDefault
v_inputInput Voltage(V)3.3
source_impedance_kohmSource Impedance(kΩ)100
load_resistance_ohmLoad Resistance(Ω)100

How It Works

Voltage Follower (Buffer)

Principle

V_out = V_in (gain = 1)

The buffer presents very high input impedance (megohms) and low output impedance (ohms). It prevents a low-impedance load from dragging down a high-impedance source.

Worked Example

3.3 V from a 100k source driving a 100 ohm load.

v_input = 3.3source_impedance_kohm = 100load_resistance_ohm = 100
  1. 01With buffer: V_out = 3.3 V (no loading)
  2. 02Load current = 3.3 / 100 = 33 mA
  3. 03Without buffer: V = 3.3 x 100 / (100000 + 100) = 0.0033 V (severe loading)

Ready to run the numbers?

Open Voltage Follower Calculator