Plotly Graph
This interactive chart plots estimated open loop magnitude response from the active gain and dominant pole inputs or the default example values.
Calculator Inputs
Use one mode at a time. The input cards below adapt to the selected calculation type.
Example Data Table
These sample engineering cases show typical open loop calculations and useful comparison points.
| Scenario | Output (V) | ΔVin (µV) | AOL (V/V) | AOL (dB) | Dominant Pole (Hz) | GBW Estimate (Hz) |
|---|---|---|---|---|---|---|
| Precision op-amp | 12.0 | 50 | 240,000 | 107.60 | 5 | 1,200,000 |
| General-purpose amplifier | 8.0 | 80 | 100,000 | 100.00 | 10 | 1,000,000 |
| High-gain stage | 15.0 | 30 | 500,000 | 113.98 | 2 | 1,000,000 |
| Wideband design | 5.0 | 100 | 50,000 | 93.98 | 100 | 5,000,000 |
Formula Used
AOL = Vout / (V+ − V−)
Vout = AOL(V+ − V−)
Gain(dB) = 20 × log10(|AOL|) and |AOL| = 10^(dB/20)
|A(f)| = A0 / √(1 + (f/fp)^2),
Phase = −tan⁻¹(f/fp),
GBW ≈ A0 × fp
These formulas are widely used for amplifier modeling, op-amp approximation, and quick design checks during analysis, troubleshooting, and frequency response estimation.
How to Use This Calculator
- Choose the calculation mode that matches your engineering task.
- Enter voltages, gain values, or frequency data in the visible fields.
- Select the correct units before submitting the form.
- Add positive and negative rails if you want clipping awareness.
- Press Submit to display the result above the form.
- Use the export buttons to download a CSV summary or a PDF report.
Why Gain Matters
Open loop gain shows amplifier sensitivity before feedback is applied. In this calculator, a 12 volt output driven by a 50 microvolt differential input equals 240,000 V/V, or 107.60 dB. That relationship explains why small input errors create large output movement. Engineers use the value to compare devices, judge sensitivity, and estimate how much closed loop accuracy depends on internal gain margin.
Ratios And dB
Voltage ratio and decibel views serve different needs. Ratio shows direct multiplication, while decibels compress large numbers into a form that is easier to compare. A gain of 100,000 V/V becomes 100 dB, and 500,000 V/V becomes about 113.98 dB. Reading both values together helps teams review datasheets, simulation outputs, and lab results without losing engineering context.
Rails And Clipping
Ideal calculations do not guarantee output swing. When predicted output exceeds plus 13.5 volts or minus 13.5 volts, clipping reduces effective gain. The calculator exposes that difference immediately. This matters during overdrive checks, startup analysis, and troubleshooting because measured gain can appear lower than expectation when the amplifier is already limited by its output stage and supply rails.
Frequency Response
A dominant pole model links DC gain to bandwidth. Using 240,000 V/V with a 5 hertz pole gives an estimated gain bandwidth product near 1.2 megahertz. As frequency rises, magnitude drops according to the single pole relation and phase shifts negative. The Plotly graph helps users see where open loop authority declines, how quickly rolloff develops, and why compensation choices influence stability margins.
Review Workflow
A workflow starts with measured output and differential input. Next, convert the result to decibels for specification checks. Then evaluate operating frequency and pole assumptions to understand rolloff. Finally, apply supply rails and confirm whether clipping changes interpretation. This sequence turns scattered measurements into a structured review method for validation reports, troubleshooting notes, and design tradeoff discussions.
Quality Checks
Accurate gain analysis depends on units, frequency entries, and correct polarity assumptions. Microvolts entered as millivolts distort results by one thousand times. Ignoring sign can hide inversion behavior. Before sign-off, verify units, recheck rail values, compare calculated decibels with expected ranges, and save exported tables for traceable documentation in laboratory records and formal reviews.
FAQs
What does open loop gain represent?
It represents how much an amplifier multiplies the differential input before feedback is applied. Very high values mean tiny input differences can produce large output changes.
Why is gain shown in both V/V and dB?
V/V shows direct multiplication, while dB makes very large gain values easier to compare. Engineers commonly use both views during design reviews and specification checks.
Why can measured gain look lower than calculated gain?
If the output reaches the supply rails, clipping occurs. Once saturation starts, the actual output no longer follows the ideal open loop equation, so effective gain falls.
What does the dominant pole frequency change?
It sets where open loop magnitude begins to roll off. A lower pole frequency reduces gain sooner, while a higher pole frequency preserves gain over more bandwidth.
Can this calculator be used for op-amp estimation?
Yes. It is useful for quick op-amp approximations, frequency-response checks, gain conversions, and clipping awareness during teaching, troubleshooting, and early design evaluation.
What inputs should I verify before exporting results?
Check unit selections, gain format, polarity, supply rails, and frequency entries. Small unit mistakes can change results dramatically, especially when microvolts or decibel conversions are involved.