Re: Why does the gyro need the ADC?
 

The only reason to run the output of a gyro or accel Threw an op amp would be to apply some signal conditioning or filtering. I believe the AD 150 and 300 development boards have a 400HZ filter already plus the ADC ports on the FRC have a RC filter also. I don't remember having any issues with noise when we where playing with the gyro's. The AD website has some app notes on changing the range on some of their sensors with op amps.

Re: Why does the gyro need the ADC?
 

noise would really depend on the surroundings and things around the gyro and cables from the gyro going to your microprocessor. Maybe if you'd coil that wire alongside your cables going to the motor, you'd start to see weird stuff happening :ahh:
Anyway the future of robotics signalling is going towards serial comms such as I2C, SPI and RS232. Not even PWM...
You may google these terms.. very useful.