a circuit that act as differential amplifier with unity gain

[anhnha]

Hi.

Could anyone tell me a circuit that act as differential amplifier with unity gain? I need one that is simple, easy to implement to cancel noise.
Thanks.

 

[zoulzubazz]

there are standard IC packages which can do this for you like the INA105, details in link

https://www.ti.com/lit/ds/sbos145/sbos145.pdf

the functional diagram in the pdf above can be used as a guideline to construct a diffrential amplifier using an opamp, but if you venture down 'making your own' route resistor matching is going to be critical.

hope this helps.

 

[Amin Khorsandi]

how do you want to cancel noise with such a circuit?

 

[anhnha]

Thank you. I want to design a power supply rejection boost circuit for my LDO as in the link below.
https://www.freepatentsonline.com/6897637.html
I use TSMC CMOS 180nm.
That circuit is too big and not easy to build.

 

[anhnha]

Now, I am thinking about a circuit that acts a bit like an inductor. It will block ac signal noise from power supply while having no effect on dc operating point. I tried to use inductor but it is too big to be implemented in an IC TSMC 0.18um. Could anyone suggest some topologies to do that?
Other disadvantage of inductor is that at low frequencies, the ac noise is not blocked significantly. At DC (0Hz) the inductor has no effect, it is only good at high frequencies. However, I want to block ac noise even low frequency (from 1Hz to 1Khz).