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AD9851 DDS module is based on DDS IC AD9851 produced by ATI company. It is used to make sine wave and square wave of different frequencies and you can control the module for different frequency output by either serial mode or parallel mode on board. What's more, the duty cycle of the square wave can be adjusted by an adjustable resistor - which changes the reference voltage of the comparator.
This module can make sine and square wave, and there are 2 sine wave outputs and 2 square-wave outputs.
Harmonics increases when frequency is over the 20-30MHz, and the waveform will be less and less clean.
Square Wave: 0-1MHz
Use 70MHz low pass filter, which makes waveform better.
Parallel and serial data input can be selected via a jumper.
The pin which makes DA benchmark is leaded out, so it is convenient to adjust the magnitude and the duty cycle of the output square wave.
Comparator reference input voltage generated by the variable resistor, and by this variable resistor, the duty cycle of square wave can be adjusted.