Free Op-Amp Gain Calculator
Calculate closed-loop voltage gain (Av), decibels (dB), output voltage, and power supply rail clipping for inverting and non-inverting op-amp circuits.
⚡ Op-Amp Circuit Topology
📊 Gain & Output Metrics
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Operational Amplifier Feedback & Gain Formulas
An operational amplifier without negative feedback has a massive open-loop gain ($A_{OL} > 100,000$). By providing negative feedback from the output back to the inverting input through resistor $R_f$, circuit designers stabilize the gain to a precise, mathematically predictable closed-loop value.
Non-Inverting Amplifier
A_v = 1 + (R_f / R_in)
Gain (dB) = 20 × log10(A_v)
The input signal enters the high-impedance (+) terminal directly, providing giga-ohm input impedance that prevents loading down weak sensor signals.
Inverting Amplifier
A_v = - (R_f / R_in)
The inverting terminal sits at a "virtual ground" ($0V$). The input impedance equals $R_{in}$. The output signal is 180 degrees out of phase with the input.
Frequently Asked Questions
What is power rail saturation clipping?
An op-amp cannot output a voltage higher than its positive supply rail ($+V_{cc}$) or lower than its negative supply rail ($-V_{ee}$). Standard op-amps (like LM358, TL072) saturate roughly 1.5V before the rail, while Rail-to-Rail Output (RRO) op-amps can swing to within millivolts of the rails.
Why do we use a Voltage Follower (Buffer)?
A voltage follower has a gain of exactly 1 ($A_v = 1$). It provides ultra-high input impedance and very low output impedance, isolating sensitive high-impedance sensors (like pH probes or guitar pickups) from low-impedance amplifier loads.
Can I run an op-amp from a single 5V USB supply?
Yes, this is single-supply operation ($+V_{cc} = 5V$, $-V_{ee} = 0V$). However, you must bias the non-inverting input at mid-supply ($2.5V$) using a resistor divider so the AC audio or sensor waveform has room to swing up and down without clipping at ground.