Operational Amplifier?

Question

can some1 describe the functioning of amplifiers briefly? what are the differences b/w an inverting & non-inverting amplifier besides dat of input aplied on diferent terminals?
what is open loop gain?
plzzz help...i need all this info badly.

Answer 1

Generally, an amplifier is any device that will convert a signal with a small amount of energy into a similar signal with a larger amount of energy. In popular use, the term today usually refers to an electronic amplifier, often as in audio applications. The relationship of the input to the output of an amplifier — usually expressed as a function of the input frequency — is called the transfer function of the amplifier, and the magnitude of the transfer function is termed the gain.

Inverting amplifier inverts a input that means that output is a inverted gain , non inverting just amplify signal without modulating.

Open loop gain is a gain without feedback. This means that Amplifier is working without any resistance.

Answer 2

"operational amplifiers" or op-amps are so called because their were first designed to perform mathematical operations electrically, like summers, multipliers, integraters and so forth in analog computers. Put 1 volt into a times 2 amplifier and you get 2 volts out. Any voltage you put in gets multiplied by two. The "operation" in this case is multiply by 2. Nowadays this usage has all but dissappeared and op-amps are used for a host of other things.
In the most basic sense, amplifiers take a signal, either a voltage or a current, and make it bigger at the output. A small signal at the input controlls a big one at the output. The gain of an amplifier is how much the signal is made bigger(amplified) at the output. A gain of 2 means the signal at the output is twice as big as the one at the input.
So take the case of a voltage amplifier with a gain of 2. If I apply 1V at input I will get 2V at the output. If I apply 2V at the input I will get 4V at the output and so on. This is a non-inverting amplifier.
Non-inverting means when the input goes positive the output also goes positive. In an inverting amplifier, if I apply 1V at the input the output will be -2V. If I apply 2V at the input the output will go to -4V. The output moves in the opposite direction of the input. This is often referred to as a gain of -2(minus 2).
An ideal op-amp has infinite gain, can move infinitely fast(infinite bandwidth), takes zero current at the input and can drive any load without a problem. Real op-amps are designed to come as close to this as possible, but fall way short.
Open loop gain is the gain of the op-amp without any external components(feedback network or load) connected to it. Op-amps are differential amplifiers, which means they amplify the voltage difference between their inverting(-) and non-inverting(+) terminals. The open loop gain is the voltage that would appear at the output if the voltage difference at the input terminals was 1V. Typically, real op-amps have open-loop gains of like 100,000. Which means than if you apply 1V to the input terminals you would get 100,000V out. Realistically, no op-amp can output 100,000V so in order to measure open loop gain you would put something more like 100uV(100 micro-volts or 0.0001V) in. This amount of gain is too much for most uses so some external circuitry is added to make the gain smaller. This smaller gain is called the closed loop gain. The term 'loop' is used because some of the output is usually looped around or fed back into the input(feedback) in order to make the gain smaller and correct for linearity problems of open-loop operation.

Hope this helps.

Answer 3

http://en.wikipedia.org/wiki/Operational_amplifier

An amplifier increases voltage. For example, an amp with a gain of 10, if you put 0.1 volts at the input, you'll get 1.0 volts at the output.

Inverting with a gain of 10: put -0.1 volt at input, get +1.0 volt at the output. Non inverting; g=10, input = +0.1v, output = + 1.0v

open loop http://en.wikipedia.org/wiki/Open-loop_gain