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 08:49:57 · 2 answers · asked by Bluean 2 in Consumer Electronics ➔ Other - Electronics
i assume they're talking about voltage gain
2006-10-01 10:37:10 · update #1
olin1963 says "It makes a difference."
What makes you think that? Gain is gain.
It doesn't matter whether you work out the gain from the output/input voltages or from the output/ipout powers, the answer will be the same - as long as the input and load impedances are the same. If they are not the same the gain shouldn't be expressed in dB.
With your figures, and with equal input and output impedances, the total input power (signal plus noise) is 1.01mW and total output power (signal plus noise) is 10.275mW, or 10.12dBm.
Why the devil did your instructor complicate matters by mentioning noise figure ...........
2006-10-01 11:43:11 · answer #1 · answered by dmb06851 7 · 0⤊ 0⤋
Since the input is given in watts, if you're going to assume anything, assume power, not voltage. But it's not a good idea to assume anything.
If the input is 1 mW and a gain of 10 dB, the output would be right about 10mW. A little math will get your the exact figure. The NF catches my attention. Those are terrible numbers. Are you sure they are right? If the input and output impedance is the same you should be able to use a little math again to compute the output in dBm.
2006-10-01 15:15:12 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Is that a voltage gain or a power gain of 10dB? It makes a difference.
WK
2006-10-01 10:15:56 · answer #3 · answered by olin1963 6 · 0⤊ 0⤋