How to calculate Vo in this inverter?

[terry_kchai]

Hi,guys
in the picture, if Vdd=5V , Vss=-5V; input Vi=±100mV, Vo=±4.5V;
When connect two resistors like this, also let Vi=±100mV, how to calc Vo now?
Thanks

 

[LvW]

Re: an inverter question

Assuming negative feedback (not clearlx shown in the picture), the overall gain is

G=1/((1/A)+Hr) with A=4.5/0.1=45 and Hr=1/11
thus
G=8.84 and Vout=0.1*8.84=0.884 volts.

 

[Audioguru]

an inverter question

If the triangle is an opamp with its non-inverting input biased at 0V then the gain is 10R/R= 10.0.

So if the input is +100mV then the output is -1.0V. If the input is -100mV then the output is +1.0V.

 

[terry_kchai]

an inverter question

LvW, How do you get this G formula, can you tell me more detail?
Thanks

 

[overmars]

an inverter question

Hei, you can find the solution in any analog text book. As it is negtive FB, we get
Af=Av/(1+Av*F), Av=45, F=1/11

Regards!

 

[LvW]

Re: an inverter question

LvW, How do you get this G formula, can you tell me more detail?
Thanks

Here is the derivation of the formula:

At the input of A two signals are combined:

Va=Vin*(R2/(R1+R2))+Vout*(R1/(R1+R2)) in your case with R1=R and R2=10R.

If you combine this equation with Vout=A*Va you can eliminate Va and arrive at the formula for G=Vout/Vin. Try it by yourself. Its the classical formula for feedback from the control theory.