Engineering Notes

POWER RF AMPLIFIERS TECHNICAL REFERENCE MATERIAL

Gain is defined as the ratio of the output power to the input power in dB. Assume that the input power is 10 mW (+10 dBm) and the output power is 1 W (1000 mW, +30 dBm). The ratio will be 1000/10 = 100, and the gain will be 10 * log 100 = 20 dB.

It is much easier to calculate gain by converting the power to dBm first, so the gain of the above amplifier will be 30-10 = 20 dB. A simple reduction will reveal the gain. In tradition, all power is read in dBm and the gain is in dB.

Example:
A low noise amp (30 dB gain) cascades with a driver amp (20 dB gain) and a power amp (10 dB gain). The total gain will be 30+20+10 = 60 dB.

Frequently Used Decibel Conversions dB Power Ratio O 1 (-1) 3 (-3) 6 (-6) 10 (-10) 13 17 20 30 1 1.26 (0.8) 2 (1/2) 4 (1/4) 10 (0.1) 20 50 100 1000

Gain Calculator Enter RF Input Power:    W Enter RF Output Power: W     Gain = dB

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