here at Analog Devices and today we're going to talk about stability.

So for example how you analyze the stability of a typical

op-amp circuit and before we can actually get

and the details and let you know a few of amps or gonna do

is we're in talk about this concept called loop gain;

very important in terms of analyzing stability. So,

let's say we have a a typical circuit here I've drawn a non-inverting

op and configuration we can represent this configuration and block diagram

form so I can take this

amplifier I can represented as block with

adult might gain a and then I can take

the feedback network and that we have with these resistors here

and the typical way to represent that is a block

with gainer beta so if I once I have this block diagram

then I can I go and copulates a

be back equation and

we're not actually in this video going ok act like this thousands of engineers

have done this before

so we're gonna skip that you have to trust 'em I A

but here is the be back equation that's pretty famous

and what gives this is the actual what's called the close loop gain up the

amplifier just basically that output referred to the input

but the the key term that we wanna

focus on his something called loop gain which is this term

right here and the reason that this term is so important

is because when it goes to -1 you'll notice that this equation blows up

as he knows that he goes to infinity another way of saying this goes to -1

is if we say that this goes to one with a 180-degree

phase shift so we do not want that to happen

and im so the next video will talk about how

we can better make sure that doesn't happen one thing that I

did want to point out is we're calling this loop gain and just don't get

confused between the

open-loop gain which is a the the amplifier

the closed loop gain have the actual

circuit itself and just plain old

loop gain which is the term that were interested in