4 Replies Latest reply on Feb 26, 2016 7:03 AM by user_373995786

    Problem with 2 PGA blocks in sequence in PSoC 5LP, CY8CKIT-059 kit.




      I think I have found a bug in PSoC Creator 3.3,


      I’m trying to make a multi electret microphone system (4), and I need to make a x16 PGA followed by a second x16 PGA and I’m getting only the gain from the first PGA.


      I wasn’t getting consistent value with the microphone so I injected a signal with VDAC8. 
      In my experience I have put one VDAC8_2 with the value:
      2304 mV
      90 Hex
      And received in the ADC_SAR_1 values between 2427 and 2496 (in the serial port terminal)


      Then made a change in the VDAC8_2 to increase 1 bit (16mV/bit)
      And received in the ADC_SAR_1 values between 2620 and 2693 or an increase of 200.


      If we 200 /16mV = 12.5 gain,


      This result shows that only the first stage of the opamp is amplifying the signal the second stage isn’t doing nothing, but the signal is passing through it. The 2 PGA's are configured with a x16 and x16 gain.


      I’m not certain but I think this is an error in PSoC Creator 3.3, I didn’t experiment with other versions. 


      I send the project in attachment.


      Thank you,


      Best regards,
      João Nuno Carvalho