I need some help. I have a homework question that I can't seem to figure out. An Amplifier has a gain of 10 db and a NF of 4.4 db. The Signal at the input is 1mW and S/N at the input is 20 db. I need to know what output power in dbm? Please help.
2006-10-01 08:59:00 · 5 answers · asked by Bluean 2 in Science & Mathematics ➔ Engineering
This is one of those problems that can be calculated exactly. What is missing is the impedance of the amplifier so that the noise power can be calculated. If you wanted to do that, as seen at http://www.ecircuitcenter.com/Circuits/Noise/Noise_Analysis/res_noise.htm
you would also have to know the bandwidth of the amplifier. The assumptions of the other answers make assumptions that with a 1mW signal input, the noise of a resistor, even a high value, and a wide bandwidth, the resistor equivalent power is insignificant. This makes the amplifier output 10 dB above the input + an insignificant amount of noise. The 20 dB s/n again is insignificant. It tells you that there is 20 dB less (1/100 power) at the input from the noise of the input signal.
Hope this helps.
2006-10-02 06:45:20 · answer #1 · answered by Joseph G 3 · 2⤊ 0⤋
The previous answer is correct, the output power is 10 dB more than the input power. Convert it back to mW:
10 dBm = 10 LOG (x/1 mW)
x = 10 mW
The noise figure or signal-to-noise ratio of the amplifier is irrelevant for finding the output power of the amplifier. Only compression or distortion due to saturation could influence the true output power.
2006-10-01 17:35:34 · answer #2 · answered by SkyWayGuy 3 · 1⤊ 0⤋
Your input power is 0 dbm, and the gain is 10 db, so the output power is 10 dbm, plus a tiny amount of noise. The noise level is negligable.
2006-10-01 09:04:25 · answer #3 · answered by cosmo 7 · 1⤊ 0⤋
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2016-11-25 20:59:55 · answer #4 · answered by ? 4 · 0⤊ 0⤋
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2014-11-04 14:31:08 · answer #5 · answered by jason 3 · 0⤊ 0⤋