Op Amps (how does it work)

Discussion in 'General Electronics Chat' started by activex, Mar 12, 2014.

1. activex Thread Starter New Member

Mar 5, 2014
3
0
Hi,

Just wondering..

Op Amps ... it amplifier the signal...but does it actually amplify the power? I mean, I know op amps has highest efficiency is 100%, that is, it amplify the input signal to have as much power as the input reference power, correct?

Anyway...so this lead to my question,

"does op amps give more output power than its input power?"

my believe is no.

any help is appriciated.

I just cannot explain how this works but i have a feeling that is how it works

2. shteii01 AAC Fanatic!

Feb 19, 2010
3,519
515
Power=I*V

Check the V and I of the input signal, calculate power.
Check the V and I of the output signal, calculate power.
Compare the two calculated values of power.

3. activex Thread Starter New Member

Mar 5, 2014
3
0
i don't have an op am to test too bad. i bet the ouput power is lower than input power

4. crutschow Expert

Mar 14, 2008
13,527
3,393
If by input power you mean the input signal power, then yes, the op amp output power can be (much) more than the input power.

If by input power you mean power for the op amp, then no, the op amp power cannot be more than the input power (and the efficiency of output power to power supply power is always less than 100%).

5. MrChips Moderator

Oct 2, 2009
12,657
3,461
No, you may be thinking of transformers where the power transfer is less that 100%.

An amplifier (or op-amp) is like a control valve. A small amount of power in can control a much larger power out.

The output power is determined by the resistance of the load. If you keep the voltage the same and reduce the load resistance you get more power.

Power P = (V x V)/ R

6. kubeek AAC Fanatic!

Sep 20, 2005
4,691
806
Then you should ask another question, what property of "the signal" does it actually amplify? Does it amplify voltage? Does it amplify current? Or both? Does this depend on how the opamp is configured and what is the load?

Also, generally speaking when you talk about input and output power, you are talking about the signal path, excluding the power supply wires that feed the opamp. So amplifier can provide more power on output than it gets from the input, and the difference is supplied by taking power from the powersupply.

7. LvW Active Member

Jun 13, 2013
674
100
...but Pout is derived mainly from the supply (as outlined in crutschow`s contribution).