Hi guys
for this circuit is't V0 due to V1 is just the non inverting circuit which is
V0 = ( 1+ R4/R3) * V1 !! Becasue that's wht it seems like but my teacher told me that Vo due to V1 is just zero !!!
any explanation please
thanks

 

opamp will do everything it can to ensure voltage difference at it's inputs is zero.

since inputs are high impedance, there i no current in or out of inputs.
using voltage divider we can write:

Vin(-) = Vo*R3/(R3+R4)

Vin(+) = Vin(-) = Vin

(Vo-Vin)/R2 = (Vin - V1)/R1

because current through R1 and R2 is same (recall - high impedance input of opamp).

then use algebraic manipulation to get Vo as function of V1 (input voltage)
should be something like this:
[Vo-Vo*R3/(R3+R4)]/R2=[Vo*R3/(R3+R4) - V1]/R1
[Vo-Vo*R3/(R3+R4)]/R2-Vo*R3/[R1(R3+R4)] = - V1/R1
Vo{1-R3/[R2(R3+R4)]- R3/[R1(R3+R4)} = - V1/R1
Vo = - (V1/R1)/{1-R3/[R2(R3+R4)]- R3/[R1(R3+R4)]}

and then (after you get correct expression that looks something like previous line) you can play with it. for example you can calculate what happens when V1=0 or when all resistors are same etc.

 

Chapter 8: OPERATIONAL AMPLIFIERS

 

Hola Bill,

Who wrote chapter 8?

Whoever the author is, he did a good job. Found it easy to follow.

 

is that document maintained? the last update was some three years ago and there is still lot of work to be done.

 

Not me, but I have written other parts of the book.

At the moment the editor is in absentia. I do expect him to eventually return though.

 

And what makes impossible to know his name?