Op-Amp Gain Calculator

Calculate gain and resistor values for op-amp circuits

Output is inverted (180° phase shift) with gain = -Rf/Rin

Circuit Formula

Vout = -(Rf / Rin) × Vin

kΩ
kΩ
V

Design Tips

  • • Use 1% tolerance resistors for better gain accuracy
  • • Keep resistor values between 1kΩ and 1MΩ for best performance
  • • Add bypass capacitors (100nF) close to op-amp power pins
  • • Consider gain-bandwidth product (GBW) for high-frequency applications
  • • Output swing is limited by supply rails (rail-to-rail op-amps help)

Understanding Op-Amp Configurations

Operational amplifiers (op-amps) are versatile analog building blocks used in countless electronic circuits. By selecting the right configuration and resistor values, you can create amplifiers, buffers, filters, and signal conditioning circuits.

Common Configurations

Inverting Amplifier

Gain = -Rf / Rin

  • • Output is 180° out of phase with input
  • • Input impedance equals Rin
  • • Virtual ground at inverting input
  • • Can achieve gains less than 1

Non-Inverting Amplifier

Gain = 1 + Rf / Rin

  • • Output is in phase with input
  • • Very high input impedance
  • • Minimum gain is 1 (unity)
  • • Better for high-impedance sources

Differential Amplifier

Vout = (Rf/Rin) × (V1 - V2)

  • • Amplifies difference between two inputs
  • • Rejects common-mode signals
  • • Useful for sensor interfaces
  • • Requires matched resistors for best CMRR

Voltage Follower (Buffer)

Gain = 1

  • • Unity gain (no amplification)
  • • Extremely high input impedance
  • • Very low output impedance
  • • Isolates high-Z sources from loads

Ideal vs. Real Op-Amps

ParameterIdealTypical Real
Open-loop gain∞100,000 - 1,000,000
Input impedance∞1MΩ - 10TΩ
Output impedance010Ω - 100Ω
Bandwidth∞1MHz - 1GHz (GBW)
Input offset voltage00.1mV - 10mV
Input bias current01pA - 1µA

Popular Op-Amp ICs

General Purpose

  • • LM741 (classic)
  • • LM358 (dual)
  • • TL072 (JFET input)
  • • NE5532 (audio)

Precision

  • • OPA277 (low offset)
  • • AD8628 (zero-drift)
  • • LTC2057 (chopper)
  • • OPA189 (ultra-low noise)

Rail-to-Rail

  • • MCP6001 (single)
  • • OPA344 (single supply)
  • • AD8605 (low power)
  • • LMV358 (low voltage)

Design Considerations

  • Gain-Bandwidth Product (GBW): The product of gain and bandwidth is constant. Higher gain reduces available bandwidth. Check GBW in the datasheet.
  • Resistor Selection: Use values between 1kΩ and 1MΩ. Too low increases power consumption; too high increases noise and offset errors.
  • Matching Resistors: For differential amplifiers, use 0.1% tolerance resistors or resistor networks for best common-mode rejection.
  • Stability: Some op-amps require compensation capacitors. Unity-gain stable op-amps are easier to use but may have lower bandwidth.
  • Power Supply: Use adequate bypass capacitors (100nF ceramic + 10µF electrolytic) close to power pins. Consider single vs. dual supply operation.