Electronics · Free Calculator
Inverting Op Amp Amplifier Calculator
Find the gain and output voltage of an inverting op amp stage, or choose the feedback resistor for a target gain.
Gain = −Rf/RinOutput voltageGain in dBResistor design
V
V
Voltage gain−4.7
Gain in dB13.44 dB
Output voltage−2.35 V
Input impedance10 kΩ
How this result was calculated
- Av = −Rf ÷ Rin = −47 kΩ ÷ 10 kΩ = −4.7
- Vout = Av × Vin = −2.35 V
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Inverting Amplifier Formula
Av = −Rf ÷ Rin
Vout = −(Rf ÷ Rin) × Vin
Zin = Rin
Vout = −(Rf ÷ Rin) × Vin
Zin = Rin
Worked example
Rin = 10 kΩ and Rf = 47 kΩ give a gain of −4.7. A 0.5 V input produces −2.35 V at the output.
Key insight: the input impedance of an inverting stage is only Rin, so a sensor with high source resistance needs a buffer or a non inverting stage instead.
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Frequently Asked Questions
What is the gain of an inverting amplifier?
−Rf/Rin. The minus sign means the output is inverted (180° phase shift).
Can an inverting amplifier have a gain less than 1?
Yes. Make Rf smaller than Rin to attenuate while inverting.
What value of resistors should I use?
Typically 1 kΩ to 100 kΩ. Too low loads the source and op amp; too high adds noise and offset from bias current.
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