Op-Amp Gain Calculator
Design Inverting and Non-Inverting Amplifier circuits.
What is an Op-Amp?
An Operational Amplifier (Op-Amp) is the building block of analog electronics. It is a high-gain differential voltage amplifier. Ideally, it has infinite gain, infinite input impedance, and zero output impedance.
By using negative feedback (connecting the output back to the input through resistors), we can precisely control the gain. This calculator covers the two most fundamental configurations: Inverting and Non-Inverting.
Formulas and Configurations
1. Non-Inverting Amplifier
The signal enters the positive (+) input. The output is "in phase" with the input. The gain is always 1 or greater.
Gain (Av) = 1 + (R2 / R1)
Vout = Vin × Av
2. Inverting Amplifier
The signal enters the negative (-) input. The output is inverted (multiplied by -1). Gain can be less than 1 (attenuation).
Gain (Av) = - (R2 / R1)
Vout = - Vin × (R2 / R1)
Practical Applications
- Audio Preamps: Amplifying a tiny 5mV signal from a microphone to a 1V line-level signal usable by a mixer.
- Sensor Conditioning: Buffering the output of a high-impedance sensor (like a pH probe or piezo) so it can be read by an Arduino ADC.
- Active Filters: Using op-amps with capacitors to create precise Low Pass, High Pass, or Band Pass filters for audio processing.
FAQ
What is "Virtual Ground"?
In an inverting config, the positive input is grounded. Because the op-amp tries to keep both inputs at the same voltage via feedback, the negative input is also held at 0V. It is not connected to ground, but it acts like it. This is a Virtual Ground.
What is "Rail-to-Rail"?
Standard op-amps (like LM741) cannot output voltages all the way to their power supply rails (e.g., with 5V supply, max out is 3.5V). Rail-to-Rail op-amps (like MCP6002) can output nearly the full supply voltage (0V to 5V), which is essential for low-voltage battery circuits.
Why do I need a dual supply (+/-)?
AC signals (like audio) swing positive and negative. If you only have a single supply (0V to 12V), the op-amp cannot output the negative half of the wave (it clips at 0V). You need either a dual supply (+12V/-12V) or to bias the signal to a "Virtual Ground" at middle voltage (6V).