how to get positive voltage using Ad8221?

[harris110]

I have question how can i get always positive dc voltage using AD8221 IC.?

 

[KlausST]

Hi,

Give to the IN+ a higher voltage than on IN-

It´s not a very specific question. Like: how can i get my car to always move forward?


Klaus

 

[harris110]

I am using at the end of a bridge and one resistance of the bridge will always change. I think now you may understand. And i have to design a PCB.

Hi,

Give to the IN+ a higher voltage than on IN-

It´s not a very specific question. Like: how can i get my car to always move forward?


Klaus

 

[KlausST]

Hi,

With that less information you can hardly build apcb.

Klaus

 

[harris110]

I have attached the circuit i hope now it will be clear. Here resistor with key C will vary.

 

[KlausST]

Hi,

No, it is not clear what you want.
If you change resistor C in a way that at IN+ is less voltage than on IN-, then the circuit must output a negative voltage.
Otherwise something is wrong.

It is like you switch ON the heating, but say you want it to become colder.
***********
The circuit amplifies the difference of the two input voltages.
Forr example on IN- you have 3.0V.
If now on IN+ is 3.1 V you will see a positive value at the output
If on IN+ is exactely the same 3.0 V then output is 0.0V
If on IN+ is 2.9V you will see a negative output.

But you don't want a negative voltage. What do you expect?
Should the value be limited at 0.0V?
Or should it go positive? This is called a rectifier.

Klaus