# 33120 arb waveform offset

Question asked by jackm on May 27, 2014
Latest reply on Jun 1, 2014 by jackm
I want to generate waveforms with small amplitude relative to the DC offset, e.g. a square wave going between 1.0 and 1.01V. The regular DC offset field is limited to twice the waveform amplitude. But the real problem is the way the 33120 scales output by the peak-to-peak range of the arbitrary waveform data. The output appears to be:

volts = amplitude * DN / (MaxDN - MinDN) + offset

For my example 1.0 to 1.01V, the best I can do is
amplitude = 0.01
offset = 0.02
MaxDN = 2047
MinDN = 2026

Then the actual output is 0.985 to 0.995 V. :(

I know about adding an external DC supply to offset the output, but is there some way to bypass the peak-to-peak range scaling? In the above example, if I create a waveform from 0.0 to 1.01V, using

amplitude = 1.01
offset = 0.505
MaxDN = 2047 (output is 1.01V)
MinDN = -2047 (output is 0V)
and DN = 2006 for output = 1.00V

There's plenty of resolution - but adding the point at -2047 will cause a glitch in the output.

Thanks for any ideas.