Op-Amp Input Offset Error
Vos_total = Vos + drift × ΔT
Quick answer
This calculator solves Vos_total = Vos + drift × ΔT for Total Offset. With Initial Offset 0.22 mV, Offset Drift 10 µV/°C, Temperature Change 50 °C, the result is 0.72 kV.
Calculator
Formula
Description
Op-amp input offset voltage is a DC error that appears as if a small voltage source exists between the two inputs. It is caused by mismatches in the input differential pair transistors. The offset drifts with temperature, adding to the initial room-temperature offset over the operating range. For precision applications like strain gauge amplifiers and current sense circuits, total offset error (initial + drift) must be much smaller than the signal being measured. Auto-zero and chopper-stabilized op-amps reduce offset to sub-microvolt levels.
Variables
- Vos_total — Total input offset voltage (V)
- Vos — Initial offset at room temperature (V)
- drift — Offset temperature drift (V/°C)
- ΔT — Temperature change from calibration (°C)
Practical Notes
Typical Vos values: general purpose op-amps 1-5 mV, precision op-amps 25-250 µV, chopper op-amps 1-10 µV. Offset drift ranges from 0.01 µV/°C (chopper) to 5-20 µV/°C (general purpose). The offset error is multiplied by the closed-loop gain, so a 1 mV offset with gain of 100 produces a 100 mV output error.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| Vos_total | Total Offset | µV | pV, nV, µV, mV, V, kV |
| Vos | Initial Offset | µV | pV, nV, µV, mV, V, kV |
| drift | Offset Drift | µV/°C | µV/°C |
| dT | Temperature Change | °C | °C |
Step by step
- 1. What you know: Initial Offset 0.22 mV, Offset Drift 10 µV/°C, Temperature Change 50 °C
- 2. The relation: Vos_total = Vos + drift × ΔT
- 3. Substitute: Vos = 0.22 mV, drift = 10 µV/°C, dT = 50 °C
- 4. Result: Total Offset = 0.72 kV
Worked examples
Minimum range
Given: Initial Offset 2.2 µV, Offset Drift 0.1 µV/°C, Temperature Change 2.5 °C
Result: Total Offset = 2.45 V
Low range
Given: Initial Offset 22 µV, Offset Drift 1 µV/°C, Temperature Change 25 °C
Result: Total Offset = 47 V
Typical
Given: Initial Offset 0.22 mV, Offset Drift 10 µV/°C, Temperature Change 50 °C
Result: Total Offset = 0.72 kV
High range
Given: Initial Offset 1.76 mV, Offset Drift 100 µV/°C, Temperature Change 85 °C
Result: Total Offset = 10.26 kV
Maximum range
Given: Initial Offset 17.6 mV, Offset Drift 1000 µV/°C, Temperature Change 850 °C
Result: Total Offset = 867.6 kV
How Total Offset changes with Initial Offset
| Initial Offset (input) | Total Offset (result) |
|---|---|
| 48.4 µV | 2.468 kV |
| 121 µV | 2.541 kV |
| 0.242 mV | 2.662 kV |
| 0.363 mV | 2.783 kV |
| 0.484 mV | 2.904 kV |
| 0.726 mV | 3.146 kV |
| 0.968 mV | 3.388 kV |
| 1.936 mV | 4.356 kV |
| 3.388 mV | 5.808 kV |
| 4.84 mV | 7.26 kV |
The same result in other units
| Unit | Value |
|---|---|
| mV | 720000 |
| V | 720 |
| kV | 0.72 |
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<p><a href="https://vbatpower.com/formulas/opamp-input-offset/">Op-Amp Input Offset Error</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Op-Amp Input Offset Error?
Use Vos_total = Vos + drift × ΔT. With Initial Offset 0.22 mV, Offset Drift 10 µV/°C, Temperature Change 50 °C, Total Offset works out to 0.72 kV.
What is the formula for Op-Amp Input Offset Error?
The formula is Vos_total = Vos + drift × ΔT. Op-amp input offset voltage is a DC error that appears as if a small voltage source exists between the two inputs.
What units does Op-Amp Input Offset Error use?
Total Offset is shown in mV, V, kV. Values are held in SI base units internally, so you can mix prefixes without converting by hand.
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