Electronics

jamescat · Joined: 09 May 2007 Posts: 3 Location: Charlotte NC

I am taking an online electronics course and I am stumped on decibel/logarithm section relating to amplifiers. My problems deal in power or voltage gain, and levels. Here are 2 examples that I cannot solve. (1) A power amplifier has a gain of 26dB, and an input of 1 volt. What is the voltage level? (2) An amplifier has a voltage gain of 60dB, the input is 10 microvolts, what is the output? I have a couple formulas, and I know the answers, but I can't figure out how to get the answers from the formulas. The answer to problem one is 20, and the answer to problem 2 is 10. Here are the formulas:

Gain= signal out/signal in

dB= 10 x log(base 10) (W out/ W in)
dB= 20 x log(base 10) (V out/ V in)

Output voltage= input level x gain ratio

I need a very detailed expression as to how to solve these problems. I have looked in two textbooks for further explanation, but I cannot find the solutions.

Thank you so much if you can help!!!!

neon · Joined: 25 Feb 2006 Posts: 570

HERE WE GO AGAIN power ratio=100-voltage and current ratio 10,000=20 db
the decibel or Db is a unit used to express the ratio between two amounts of POWER p1and p2 existing at two points
by definition #db=10 log 10 p1/p2 power
or I or V as #Db 20 log v1/v2 voltage
or #Db 20log I1/I2 current
i do asune that you know how to get the logs of those nunbers. otherwise take mathemtics first.

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