Difference amplifier
Difference amplifier with circuit equations and operating-limit checks.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Exact transfer: Vout = (1 + R2/R1′) R4/(R3′+R4) V+ − (R2/R1′) V−
Differential/common-mode gains: Gd = (G+ − G−)/2; Gcm = G+ + G−
Assumptions
- The ideal linear solution is reported without clipping. Operating-limit warnings indicate where it is not physically achievable.
- At levels 3–6, entered values describe a generic voltage-feedback amplifier; these are not guaranteed specifications for any particular device.
- R1′ and R3′ include source impedances. CMRR tolerance expression is the small-tolerance worst-case approximation for nominally matched ratios; use the exact common-mode gain for the entered resistor values.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Positive signal input
- 1.1 V
- Negative signal input
- 1 V
- Negative input resistor R1
- 10000 Ω
- Feedback resistor R2
- 100000 Ω
- Positive input resistor R3
- 10000 Ω
- Positive ground resistor R4
- 100000 Ω
- Negative source impedance
- 0 Ω
- Positive source impedance
- 0 Ω
- Monte Carlo trials
- 2000
- Monte Carlo seed
- 42
- Model level
- 1
- Independent resistor tolerance
- 1 %
- Operating temperature
- 25 °C
- Feedback resistor TCR
- 25 ppm/°C
- Input resistor TCR
- 25 ppm/°C
- Positive supply
- 15 V
- Negative supply
- -15 V
- Output rail headroom
- 1 V
- Maximum input common-mode voltage
- 13 V
- Minimum input common-mode voltage
- -13 V
- Output load
- 10000 Ω
- Maximum linear output current
- 0.02 A
- Non-inverting source resistance
- 100 Ω
- Input offset bound
- 0.0005 V
- Offset drift bound
- 0.000002 V/K
- Non-inverting input bias current
- 2e-8 A
- Inverting input bias current
- 2e-8 A
- DC open-loop gain
- 100 dB
- Common-mode rejection
- 100 dB
- Power-supply rejection
- 100 dB
- Supply change
- 0.1 V
- Gain-bandwidth product
- 1000000 Hz
- Slew rate
- 500000 V/s
- Signal frequency
- 1000 Hz
- Input peak amplitude
- 0.1 V
- Input voltage white noise
- 1e-8 V/√Hz
- Input current white noise
- 1e-12 A/√Hz
- Voltage-noise 1/f corner
- 10 Hz
- Noise integration low frequency
- 1 Hz
- Noise integration high frequency
- 20000 Hz
- Open-loop output resistance
- 50 Ω
- Inverting input capacitance
- 5e-12 F
- Load capacitance
- 1e-10 F
- Output isolation resistor
- 0 Ω
- Additional open-loop pole
- 10000000 Hz
Results
- Ideal output
- 1 V
- Signal gain
- 10
- Noise gain
- 11
- Common-mode gain
- 0
- Resistor CMRR
- Infinite for exact ratio match dB
- Resistor-tolerance CMRR bound
- 48.7867 dB