There are several approaches to amplify –
1) Use external transconductance OpAmp and IDAC in PSOC to control its G.
2) Use A/D then multiply its values by desired G, and pass back to VDAC. This
Approach constrained to 8 bit precision by VDAC.
3) 2) but use PWM to create DAC, BW limited approach.
4) Use PGA and control ist G setting. However it has limited G resolution, 9 G’s
between 1 and 50 available. Basically 3 bits resolution.
I dont want to use method 2 since that will require unnecessary conversion from analog to digital and digital to analog
Is there a way I can use method 3 i.e. use a PGA but still get other gains of 1, 3, 5, 6 etc?
Please elaborate on method 1.
The PGA comes only with fixed gain settings.
For transconductance amplifiers, see e.g. at TI. There you can also find variable gain amplifiers and multipliers, which might also help you.
Can you explain a little bit more why you need such a fine control over the amplification? I would have guessed that the gain settings of the PGA are enough for most cases...
That's right but my problem demands that as i move the capsense slider, the gain shd increase evenly... not in jumps..
Also, can you help me a little on adding an offset on button presses. I want that just as I press a capsense button, my input wave shifts either up or down depending whether the right or left button is pressed
Here are some V controlled solutions -
Using JFET to control G. Use depletion mode FETs for + control V.
Use multiplier -