Vref in PGA

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Anonymous
Not applicable

What is the significance of providing Vref input in PGA?Is it the same as 'Vin-' in case of differential amplifier ?

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ETRO_SSN583
Level 9
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t its most basic level PSOC is a single supply device, hence so is

   

it's analog. The PGA is a NI amplifier, and in a single supply system

   

often one needs offset to maximize dynamic range. PGA looks like -

   

 

   

   

 

   

And its Xfer function looks like

   

 

   

   

 

   

Where Vgnd = Vref. Using this approach, designing with a specific analog ground

   

point, one can also see that this also minimizes offsets due to ground current drops.

   

 

   

Regards, Dana.

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ETRO_SSN583
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Where I stated "Where Vgnd = Vref. " Vref is the output of the reference mux

   

attached to Ra.

   

 

   

Regards, Dana.

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ETRO_SSN583
Level 9
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Just realized I thought I was in PSOC 1 forum.

   

 

   

The general comments apply, just the reference mux is a little different, eg. the

   

inputs available to it.

   

 

   

Regards, Dana.

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Anonymous
Not applicable

Can I use it as a differential amplifiier?

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ETRO_SSN583
Level 9
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The PGA is really a single ended amplifier.

   

 

   

If ultimately you are feeding signal to ADC, keep in mind the DelSig has a

   

diff input, and a gain block, up to a G = 8. If you need more gain then look

   

at http://www.psocdeveloper.com/forums/viewtopic.php?f=42&t=5806

   

Do not use the PGA approaches to a diff amp, their gain error swamps out

   

their ability to provide decent CMR. The author is going to update this and drop

   

PGA based solutions.

   

 

   

There are some references I posted here that are useful, mainly doing a

   

design with OA's (2 - 3) and a precision resistor array.

   

http://www.psocdeveloper.com/forums/viewtopic.php?f=42&t=5806

   

 

   

Regards, Dana.

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