Hi Kai,

1. I simulated the cricuit using Circuit maker 2000. The outputs waveforms are very nice but after every cylce the output is going slightly below 0V line i.e. The magnitude of this is approx. -15mV. Do I need to use clamp diodes for ADC input protection?

2. I am using I2C ADC PCF8591 for the waveform digitization this ADC has Analog GND input so I am planning to use two Ground Plane on my board. Analog Gnd Plane and Digital Gnd Plane. Thus I will be laying the Op-Amp ADC etc on upper half of the board and logic circuitary such as micro 74HC' in lower half. Thus upper half I will draw a Analog Gnd and lower half digital Gnd Plane. Now I want to know that. Should the op-Amp be in the sea of Analog Gnd Plane or outside it. I will keep the AGND and DGND planes totally separate and will join them only at the supply input terminal Is that fine or it is necessay to join them at ADC? My current scheme is shown below.



Thanks & Regards,
Prahlad Purohit