Power Added Efficiency Calculator computes PAE, drain efficiency, amplifier gain, and thermal dissipation for an RF power amplifier from input, output, and DC supply power values.
Power Added Efficiency Calculator for RF Amplifier True Efficiency
This tool computes Power Added Efficiency (PAE) for an RF power amplifier, accounting for the drive power the amplifier needs at its input rather than just comparing output to DC power. RF and microwave power amplifier engineers use it to characterize real amplifier efficiency and to compare designs on equal footing when checking datasheet claims.
Reading the PAE Calculator Inputs and Outputs
Enter RF input power, RF output power, and DC input power (VDC × IDC), all in watts. The calculator returns PAE, drain efficiency, amplifier gain, thermal dissipation, and the gap between PAE and simple drain efficiency.
Power Added Efficiency Formula
PAE is defined consistently across RF power amplifier engineering references, including Analog Devices’ engineering documentation and standard RF/microwave textbooks, as the added RF power relative to the DC power consumed:
$$PAE = \frac{P_{out}-P_{in}}{P_{DC}} \times 100\%$$
Drain (or collector) efficiency ignores the input drive power entirely:
$$\eta = \frac{P_{out}}{P_{DC}} \times 100\%$$
Thermal dissipation follows from energy conservation — both the DC supply and the RF drive signal put energy into the device, and whatever doesn’t leave as RF output is dissipated as heat:
$$P_{diss} = P_{DC} + P_{in} – P_{out}$$
The most common input mistake is treating drain efficiency and PAE as interchangeable. They converge only at very high gain; at low gain they diverge sharply — an amplifier with 50% drain efficiency but unity gain (output barely exceeds input) has a PAE near zero, since almost none of the output power was actually “added” by the device.
PAE, drain efficiency, and linear gain $G=P_{out}/P_{in}$ are tied together by one identity worth knowing: $PAE = \eta\left(1-\dfrac{1}{G}\right)$. With $\eta=50\%$ and $G=10$ here, that’s $50\% \times (1-0.1) = 45\%$ — matching the calculated PAE exactly.
This is also exactly what “PAE Penalty” represents: it’s $\eta/G$, the slice of drain efficiency that gain fails to convert into true added efficiency. At high gain that penalty shrinks toward zero; at low gain (an amplifier being driven hard relative to its output) the penalty can dominate and make PAE far worse than drain efficiency alone would suggest.
PAE Power Flow Diagram
Power Added Efficiency FAQs
Why can PAE be much lower than drain efficiency?
PAE subtracts the input drive power before dividing by DC power; drain efficiency doesn’t. At low gain, most of the “output” power is really just the input signal passing through, so PAE correctly reports very little was actually added.
What DC power should I enter if the amplifier has separate supply rails?
Sum every DC supply the device draws from (for example, both gate and drain bias, or base and collector supplies). Leaving one rail out understates $P_{DC}$ and makes PAE look better than it actually is.
Can PAE exceed drain efficiency?
No. Since $PAE = \eta(1-1/G)$ and gain $G$ is always greater than 1 for an amplifier, PAE is always less than or equal to drain efficiency, only approaching it as gain gets very high.
Do I need dBm or watts for these inputs?
Watts (linear units) for the calculation itself. The calculator also reports the dBm equivalents for input and output power, but PAE, efficiency, and gain math all require linear values, not decibels.
Why does thermal dissipation matter alongside PAE?
Thermal dissipation sets cooling requirements directly, in watts. Two amplifiers with the same PAE can need very different heatsinking if their absolute power levels differ, since dissipation scales with total power, not just the percentage.