What is the significance of providing Vref input in PGA?Is it the same as 'Vin-' in case of differential amplifier ?
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.
Where I stated "Where Vgnd = Vref. " Vref is the output of the reference mux
attached to Ra.
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.
Can I use it as a differential amplifiier?
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
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.