Basic questn on opamps

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raj1994

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if any opamp or amplifier gains the input signal doesnt that means it convert very low poer signal into a high power signal......if power amplifier....
like 741 opam has gain of 10^5
that means its convert a signal from micro volts to volt range.....where does this power comes from....how this amplification is possiblee.....doesnt it raises questn over basic law of energy conservation....?
pls clarify
 

As described in this Wikipedia article https://en.wikipedia.org/wiki/Amplifier
the energy required to increase the signal amplitude and power is taken from an external energy source. This is a common property of all kind of electronical, optical or mechanical amplifiers. Law of energy preservation is always fulfilled.

In case of an OP like uA741, the V+ and V- terminals are supplying the external energy.
 
If you look at the graph of frequency response on the datasheet for an opamp you will see that it cuts frequencies above about 10Hz for a 741 opamp.
Its typical open-loop gain is 200,000 times from DC to 10Hz. At 10kHz its open-loop gain is typically 100 and at 20kHz it is only about 20 times. The 741 opamp is 47 years old and was not designed for audio frequencies.

The cutting of high frequencies is called "frequency compensation". It is used so that at a high frequency of about 1MHz and higher where the phase shifts in the circuit change negative feedback into positive feedback then the gain is less than 1 so it does not oscillate.
 

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