You could multiplex your input-signals to one OpAmp. this would take a reasonable time to stabilize, but you did not tell yet how much the frequency of the signals is. Wouldn't be too bad, when you tell us a bit more about what you want to perform.
If you mux a charge mode amp, since its corner frequency usually quite
low, there are very long settling times. Google "charge mode amplifier",
there are quite a few hits, TI, LTC, AD all have ap notes.
So take this into consideration.
If I mux multiple piezo sensors to single op-amp, I think I should wait the state of the charge amp discharged.
Can I use a swich ( instead of feedback resistor ) to instantly discharge feedback capacitor to reduce discharge time ?
Does PSoC provide the switch function? or Can I implement it with a discrete device outside of PSoC.
You can program io-pins on the fly to be Hi-Z or connected to gnd, so this is like a switch as you need it. Beware of the restricted pin-routing capabilities of a PSoC4, so have all your IO's ready and working before you start to manufacure your pcb.
Yes by using an open drain output to ground cap or
use an internal mux terminated in Vss. The former
approach has a much lower switch R than a mux.
So tradeoff is
open drain mux
lower Rdson higher Rdson
higher discharge spike lower discharge spike
shorter discharge time longer discharge time
I am trying to interface piezo sensors too.
Can you please shate with me the ampifier circuit? and the code?
Did the "muxing" worked?
Unfortunately, I stopped my project for interfacing multi-piezo sensors.
but if you have any question, I would like to be your help.
Thanks for your want to help:)
I am trying to interface piezo disk to psoc 3 . I built an amplifier that works great but when I am inputing a piezo it behaves strange. I am aware to the specs of the piezo and had learn ( a lot of google) that the best interface is charge amp with big resistanse load. I saw you made one:)
Just want to see :)
If you can please attache the schematics or tel me how you bias the "big resistance load"
Piona, on the other thread I did another config, using a Piezo, got ~ 1 V pk-pk
out if it.
unfortunately again, I cannot upload the files because my company is monitoring network..
but I think following information would be helpfull.
* for charge mode amp
Rf (Feedback R) : 10 MOhm
Cf (Feedback C) : 0.05 uF
opamp reference voltage : Vcc/2
vout = -Q/Cf + Vcc/2
Q : charge generated from sensor, I tested a pvdf film so your piezo disk needs another Cf
Time constant : Rf*Cf, so you need to change Rf again
* reference link ( chapter 3.2 )
Signal Conditioning Piezoelectric Sensors from TI