So similar to as before if you saw my previous post I am using an ad5293 digipot to control the gain of an op-amp. I previously had a bias voltage for the op-amp to offset the signal. I removed this voltage and tried amplifying DC for a simpler test. However when I put 1V dc in I get 5V out even when I set the gain to 2 and have tried with different gain values and is still 5V on output
to calculate the gain I rearranged the gain formula for RF so RF = (G-1)*Rin where G is Gain RF is feedback resistor (digipot) and Rin is my input resistor (4.3K currently but designed for 2K).
After I have the RF value I use the formulas from the ad5293 datasheet and rearrange for D (the 10 bit spi code)
and then now i have the 10bit code you need to send 16 bit words. The first 2 bits are always 0 and then the control bits 0001.
So my binary that I send for this gain is 00 0001 0011011100
so overall I am unsure why this is at 5V as i no longer have the bias voltage for the offset so that is no longer being amplified. And I am just trying to amplify dc so the issues with sine wave clipping on negative due to single supply not being relevant.
How is it inverting? isnt it exactly the same as this, as I have Rin connected to -in and RF (digitpot RH and RW) are connected the same as in the diagram and then I input my signal to the +in pin.
Any clarification would be great.
Edit: attached as file incase image isnt working cause cant see it from my end
I see -- "No Caps", missed it.
AD5293. It's in the clear.
You've established your digipot foundation (placing the ohmmeter there, send data etc. for ohms up and ohms down)?
Same schematic with the 5V supply here is the image but unless I am being stupid I am sure this is a non inverting.
Only added the changes to reflect my bodge job, meaning no LV_Adj as i cut this track and the gnd on the otherside of the resistor.
yes I can control the digipot but hard to measure the resistance with DMM as its soldered to the circuit, and obvs when powered off there it doesnt keep the set resistance.
Also should add that I could see the voltage change when in potentiometer mode for the ones not relevant to the gain so I assume the hardware is correct, and atleast the code for potentiometer mode was correct