2138Views3Replies

# How Op Amps work?

I was wondering if anyone could explain how an op amp like the LM741 works. I don't mean I want to know what's going on inside it, but more along the lines of "how can it be wired up?" and "what could it be used for?"

## Discussions

I think this page,

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

is as good a place to start as any.

Mostly op-amps are used for doing simple math-like manipulations of analog signals. For example, an amplifier gives an output that is a constant (>1) multiple of the input of the input signal. An adder adds two, or more, signals together. An integrator gives an output that is the time integral of its input.

Another popular op-amp circuit is an op-amp as relaxation oscillator. That one is also on the same page I linked above.

By the way, most of these introductory op-amp circuits assume you are using a double-sided supply, typically one with rails at +15V, ground=0, and -15V.However it is often desirable to build a circuit with op-amps that can run from a single sided supply, e.g. just +12V and ground=0. For me the usual trick for dealing with that is to just wire one of the op-amps (e.g. LM324 has 4 op-amps per chip) as a follower following a voltage divider set to half the supply. Then I've got a nice stable node at half the supply voltage (e.g at +6V for a +12V supply), and I can use that as reference for my other op-amp circuits.

Another warning is that many op-amps want a wide supply voltage range to work with. If you want your op-amp to work in a very narrow supply voltage range, e.g. +3V and ground=0, those op-amps seem to be more rare. So you have to make sure to check the data sheet first, to see if it can do that.

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

Look it up: Its a universal building block in analogue circuits. Originally it was used to create mathematical Operations in analogue computers, so you can use it to multiply add and subtract analogue voltages with them.

The multiplication and adding bits are commonly used today in all kinds of circuits from audio to motor control.