Precision Rectifier using PSoC® 3 AN59649 Not work correctly

[Anonymous]

Hi,

   

 I am trying to use precision rectifier shown in AN59649 but in my opinion it not work correctly.

   

Negative half of sine doesn't has gain -1.  Positive half sine gain is correct.

   

I attach input (CH I, red) and output (CHII, blue) oscillogram.

   

Hardware: PSoC3 CY8C3866LTI-030

   

Pins: Input_sine - P0.0 (48), outp - P0.5(54), Reference - P0.1(49)

   

External Input_sine pin connected to Reference pin via 10k resistor.

   

All input and output have DC votage 2.5V (Vdda/2)

   

Input signal sin, 200kHz, 3Vpp connected via 100nF capacitor.

   

Power supply:

   

Vdda=Vddio0=5V

   

VddD=Vddio1=Vddio2=Vddio3=3.3V

   

I check comparator output, it's correct.

       

Question:

   

How make correctly working precision rectifier?

       

Best Regards,

   

  Zbigniew

[Anonymous]

 Hi,

   

Can you change the resistance from 10k to 100 ohm and check your waveform output. The input impedance of the recitifier is low in the inverting configuration and the 10k might load the input resistor

       

Regards,

   

Praveen

[Anonymous]

Thanks,

   

It helps.

   

Best regards,

   

  Zbigniew