100-200 mV Glitch at Zero Crossing of the 44726A

When outputting a repetitive waveform, a glitch can occur near the zero crossing. The glitch is caused by a major transition of the DAC and is unavoidable. The major transition is a characteristic of most DACs. Each bit of the DAC can be thought of as a current source. Each current source is weighted in a binary fashion. For a 12-bit DAC a full scale positive output would be represented by 0000,0000,0000 and full scale negative is represented by 1111,1111,1111. When the DAC is making a transition from a positive output to a negative output, the DAC must output a 0111,1111,1111 followed by a 1000,0000,000. That is, eleven sources have to turn off and the largest source has to turn on. Timing is critical! If the most significant bit is slow turning on, 0000,0000,0000 is output -- a full scale positive output. If the MSB turns on to quickly then 1111,1111,1111 is output, which represents a full scale negative output. Likewise, glitches will occur at other transition points, such as 0011,1111,1111 to 0100,0000,0000. These glitches are smaller, but are easy to see with a distortion analyser. Executing the FILTER ON command will decrease the magnitude of the glitch by a factor of 10.