# Different sampling rates for half and full channels on oscilloscope? How is it done?

In the documentation for the Keysight DSOX1204G, it has the interesting note for the sampling rate of:

2 GSa/s (half channels)
1 GSa/s (all channels)


So, if I use all 4 channels on the scope, I get GSa/s, and if I use only two channels I get 2 GSa/s. I would assume at the core of the scope there's some low resolution ADC with a convert line that is tied to a 1GHz signal. For the 2 GSa/s are they just tying two ADCs together at the inputs but putting the convert lines 180 degrees out of phase, or is it something more interesting?

• Yes, current scopes work by having multiple slower rate ADCs (with fast analog bandwidth) which can cooperate to take samples at a higher rate for a given channel, or be assigned to different channels. For a given model (cost) you can operate it to maximize speed or channels, or you buy a different more expensive model with a different product of rate * channels. – Chris Stratton Jan 10 at 1:41