3 Replies Latest reply on Jun 22, 2020 5:55 PM by MoTa_728816

    Opamp Example Project

    EfAv_4380776

      Hello everyone.
      I've been trying to implement a non-inverting amplifier for a couple of days without any success.

      The kit I'm using is the PSoC 4200-BLE kit, CY8C4247LQ-BL483.

       

      This is the example Opamp project I'm evaluating:

       

      OpampPsoc.PNG

       

      The input signal:

      inputOpamp.PNG

       

      The yellow is the input signal and the blue one the output.

      opamp_osc.PNG

       

      The thing is I've noticed the Vout hasn't the same frequency as the input signal. Furthermore, the oscilloscope can't even read it because it seems to change randomly.
      This was the best result I could get and it was using 800mV sinewave as the Vin+. If I change this value, the Opamp doesn't amplify at all.

       

      For example using 200mV as input:

       

      200mV.PNG

       

      Any ideas of why isn't it working properly?

       

      I get that the Opamps inside the PSoC are single supplied so they can't amplify the negative side of the sine wave and the top of the output gets clipped because of the reference Voltage. Is it possible to change Vref from 3.3V to 5V internally so the Opamp can amplify up to 5V?

       

      Thanks!

        • 1. Re: Opamp Example Project
          BoTa_264741

          efav,

          You have ground loop so your 1kHz is floating against PSoC voltage at 50Hz. Thats why you see those splashes of outputs. You must connect the grounds of PSoC board and sine generator

           

          Secondly, the sine generator provides +/- voltage centered around 0V, but the Opamp has reference voltage Vss=0, so only positive half of the Sine will be amplified. 

          /odissey1

          1 of 1 people found this helpful
          • 2. Re: Opamp Example Project
            EfAv_4380776

            Hello BoTa, I've connected Oscilloscope Channel1(-), Channel2(-) and  Oscilloscope GND to the dev kit board's GND.
            Still no success, now this is what I get:

            new.PNG

            new2.PNG

             

            thanks!!

            • 3. Re: Opamp Example Project
              MoTa_728816

              Hi,

               

              I tried this with CY8CKIT-044 (CY8C4247AZI-M485).

               

              I noticed that there were a few points we can make mistakes

              (1) Vout is needed to be an Analog Pin instead of a Digital Output Pin.

              (2) Output of the Opamp must be "Output to pin."

              (3) In the main.c, Opamp_Start() must be called.

               

              IMG_4300.JPG

              I copied your schematic

              001-circuit.JPG

              Vout

              Note: Vout is not a Digital Output but another analog pin Flipped Horizontally

              002-Vout.JPG

              Vplus and Vminus

              003-Vplus.JPG

              004-Vminus.JPG

               

              Opamp

              005-OpAmp.JPG

              Pins

              006-pins.JPG

              main.c

              007-main_c.jpg

              Oscilloscope waveforms

              Note:

              The upper RED signal is the source 0.8Vp-p 1kHz Sine Wave generated by FRDM-KL25Z.

              The lower Yellow signal is the Vout

              both has 0.5V unit.

              IMG_4299.JPG

               

              moto

              P.S. I tried to intentionally made the mistakes above.

              (1) and (2) could not be compiled.

              (3) the result waveform looked like your waveform. (Output was flat)

              2 of 2 people found this helpful