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Op-Amp Gain and Active Filter Designer: Amplifier Configs, Filters and Feasibility Checks

Getting the gain right on an op-amp circuit is only half the job – you also need to confirm your chosen op-amp can actually handle the frequency and signal swing, which is exactly where many designs go wrong. This tool covers four amplifier configurations (inverting, non-inverting, differential, summing) with standard E24 resistor matching, single-pole active RC filters (low-pass, high-pass, band-pass) with a response plot and then checks whether your op-amp’s Gain-Bandwidth Product (GBW) and slew rate are sufficient – all in one place instead of switching between three separate calculators.

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How to Use

For Amplifiers:

1. Select the configuration: Inverting, Non-Inverting, Differential or Summing.
2. Enter the resistor values (Rin, Rf, or R1/R2) and optionally an input voltage to see output.
3. Review the calculated gain, plus the nearest standard E24 resistor suggestion.

For Filters:

1. Select filter type: Low-pass, High-pass or Band-pass.
2. Choose Forward mode (enter R and C to find cutoff) or Reverse mode (enter target cutoff and capacitor to get R).
3. View the cutoff frequency (or resistor) and the frequency response plot.

For Feasibility Checks:

1. Enter your op-amp’s GBW (MHz) and slew rate (V/µs) from the datasheet.
2. Enter your circuit’s gain, max signal frequency and peak voltage.
3. The tool tells you if your op-amp has enough margin or if it will distort your signal.

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Key Features

• Four amplifier configurations: Inverting, Non-Inverting, Differential and Summing
• Automatic nearest E24 standard resistor suggestion for every calculated resistor
• Active RC filter design (Low-pass, High-pass, Band-pass) with forward and reverse modes
• Visual frequency-response plot (log-scale) for the designed filter
• GBW feasibility check – tells you if your op-amp handles your gain at your signal frequency
• Slew rate feasibility check – flags distortion risk at your peak voltage and frequency
• Shows exact margin (how many times over/under requirement) for both checks
• Export as PDF or copy the result

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Formula / Logic Used

Amplifier Gain

• Inverting: $A_v = -\dfrac{R_f}{R_{in}}$
• Non-Inverting: $A_v = 1 + \dfrac{R_f}{R_{in}}$
• Differential (balanced): $A_v = \dfrac{R_2}{R_1}$
• Summing: $V_{out} = -R_f\left(\dfrac{V_1}{R_1} + \dfrac{V_2}{R_2} + \dots\right)$

Active Filter Cutoff Frequency$$f_c = \frac{1}{2\pi R C}$$

For band-pass, two RC stages set the low and high corners, then:$$Center\ Frequency = \sqrt{f_{low} \times f_{high}}, \qquad Bandwidth = f_{high} – f_{low}$$

GBW Feasibility Check$$Required\ Frequency = Gain \times Max\ Signal\ Frequency$$

Feasible if the op-amp’s rated GBW ≥ this value; the tool shows the exact margin.

Slew Rate Feasibility Check$$Required\ Slew\ Rate\ (V/\mu s) = 2\pi \times f_{max} \times V_{peak} \times 10^{-6}$$

Feasible if the op-amp’s rated slew rate ≥ this value.

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Who Should Use This Tool

Diploma and B.Tech ECE students designing and analyzing op-amp amplifier and filter circuits. Also useful for hobbyists and engineers who want a quick gain + bandwidth + slew rate sanity check before building or simulating.

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Frequently Asked Questions (FAQs)

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Related Tools

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• PCB Trace Width Calculator – plan the board layout once your circuit is finalized
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