Calculator Input
Formula Used
Non-inverting ideal gain: Av = 1 + Rf / Rg
Inverting ideal gain: Av = -Rf / Rin
Feedback factor: beta = Rg / (Rf + Rg)
Finite non-inverting gain: Av = Aol / (1 + Aol × beta)
Finite inverting gain: Av = -Aol × Rf / (Rf + Rin + Aol × Rin)
Gain in decibels: Gain dB = 20 × log10(|Av|)
Closed-loop bandwidth: BW = GBW / noise gain
Slew rate: SR = 2 × pi × frequency × Vout peak
How to Use This Calculator
Choose the amplifier model first. Enter resistor values and select the resistor unit. Add input voltage, open-loop gain, supply rails, and bandwidth data. Press the calculate button. The result appears above the form. Use CSV or PDF buttons to save the calculation.
Example Data Table
| Model | Rf | Rg or Rin | Ideal Gain | Vin | Ideal Vout |
|---|---|---|---|---|---|
| Non-inverting | 90 kΩ | 10 kΩ | 10 V/V | 0.10 V | 1.00 V |
| Inverting | 47 kΩ | 10 kΩ | -4.7 V/V | 0.20 V | -0.94 V |
| Voltage follower | 0 | 0 | 1 V/V | 2.00 V | 2.00 V |
Closed Loop Voltage Gain Guide
Why Closed Loop Gain Matters
Closed loop voltage gain is one of the most useful amplifier values. It shows how much an input signal is multiplied after feedback is applied. Open loop gain is very high in many operational amplifiers. Yet practical circuits use feedback resistors to set a stable value. This calculator helps compare that stable value against finite open loop behavior.
Non-Inverting Gain
In a non-inverting amplifier, the input reaches the positive terminal. The feedback network returns part of the output to the negative terminal. The ideal gain equals one plus feedback resistance divided by ground resistance. This makes the circuit useful when a positive output phase is required.
Inverting Gain
In an inverting amplifier, the input enters through the input resistor. The feedback resistor connects the output to the summing node. The ideal gain is negative feedback resistance divided by input resistance. The negative sign means the waveform is inverted.
Finite Open Loop Effects
Real amplifiers have finite open loop gain. They also have limited gain bandwidth product. Because of that, the actual gain can be slightly lower than the ideal value. The error becomes larger when the noise gain is high. It also grows when open loop gain is not large enough.
Output Checks
The calculator includes input voltage, supply swing, signal frequency, and headroom. These values help estimate output voltage, clipping risk, bandwidth, and slew rate. This is useful before building filters, sensor stages, audio preamps, and control loops.
Design Tips
Use matched resistor units when possible. Choose kilo-ohms for most small signal op-amp circuits. Very low resistor values waste current. Very high values may increase noise and bias current errors. After calculating, check both gain and output limit. A correct gain is not useful if the amplifier clips or lacks bandwidth.
Advanced Review
For advanced design, compare ideal and finite gain. A small percentage error usually means the feedback loop is strong. A high loop gain gives better linearity, accuracy, and stability. Still, layout, load, capacitance, and op-amp phase margin should be reviewed in real hardware.
Report Use
The download buttons support quick documentation. CSV fits spreadsheets and lab notebooks. PDF works well for reports and design reviews. Save the inputs with the results. That record helps compare resistor changes, tolerance studies, and frequency choices during later troubleshooting. Use the notes field for project context.
FAQs
What is closed loop voltage gain?
Closed loop voltage gain is the voltage gain after feedback is applied. It is usually set by external resistors, not by the raw open-loop gain of the amplifier.
Why is open-loop gain included?
Open-loop gain helps estimate real gain error. Ideal formulas assume infinite open-loop gain. Real devices have finite gain, so the practical result can be slightly lower.
What is beta in feedback?
Beta is the feedback factor. It shows the fraction of output voltage returned to the input comparison node. Lower beta usually means higher closed-loop gain.
What does gain in dB mean?
Gain in dB expresses voltage gain on a logarithmic scale. It is calculated with 20 times log base ten of the absolute voltage gain.
Why is inverting gain negative?
The negative sign shows phase inversion. The output waveform is 180 degrees out of phase with the input waveform in a standard inverting amplifier.
What is noise gain?
Noise gain is the gain seen by input offset and internal noise sources. It is important for bandwidth, stability, and finite open-loop gain error estimates.
How does bandwidth affect gain?
Higher closed-loop gain usually reduces bandwidth. A common estimate divides gain bandwidth product by noise gain. Real results depend on the amplifier model.
What does clipping check mean?
The clipping check compares estimated output voltage with supply swing limits. If output exceeds the limit, the amplifier may distort or flatten the waveform peaks.