# Cypress Developer CommunityTM

## minimum-voltage to PGA

Summary: 4 Replies, Latest post by Bob Marlowe on 03 Dec 2011 11:04 AM PST
User
39 posts

hi in PSoC1 what is the minimum voltage required by the PGA in order to amplify the signal.

if i am giving 0.01mv is it going to amplify this voltage?

Thanks and Regards

V.Vishnu Kumar

Cypress Employee
223 posts

There is nothing like minimum voltage for a PGA to amplify.  A PGA is nothing but an OpAmp and will amplify the signal however tiny it may be.  If the PGA gain is set to say 24 and the input votlage is 1mV, then the PGA will amplify this 1mV to 24mV.   The only think you have to take into consideration is that the offset voltage of the PGa also will get amplified by the same gain, but can be gotten rid of by using various calibration techniques.  Check AN2226 for one such technique.

Best Regards,

Ganesh

User
39 posts

hi

User
3 posts

Hmm. I have punched my nose few times with the PGA.

What I am really missing, is realistic numbers [minimum input Voltage] etc describing the whole PGA OPA, as it always used to be desribed by different companies like Analog Devices. The desription in the PDF is quite poor.

There is nothing to hide. Everybody knows it is not going to work with 0 Volts input. It is not RRIO PGA. But is it 50mV or 70mV or 150mV ? Exactly. The note might give relief to Cypress support, and the user as well. Thanks

User
9277 posts

Hi Dave,

I'm afraid you didn't understand neither the last answer not the way a(ny) PGA or OPAmp works! There is a datasheet describing the electric capabilities of the PGA like a datasheet for any other OPAmp, you just ought to read and understand it.

There is a (simple) mathematical formula that describes the dependence of the input and output and under the premission of an analog device (which it is) there is the lowest input value 0V in respect to VGnd and the maximum VDD (if the gain is <= 1)

So where is your mis-understanding of the physical and/or electronical capabilities of a gain-controlled OPAmp?

Have fun

Bob