8-bit R2R DAC

235

02:57:05

Getting rid of that spike was a little tricky. The upper pair of FETs function as an analogue switch, the lower pair are the inverter to drive it. They are connected to be on when the clock is low, after the spike is done.

I added an anti-aliasing filter, but I don't think it's really needed with the switch arrangement. Edit: At least the capacitor is needed, to retain charge when the switch is off. It also smooths a little spike resulting from the FETs' capacitance.

published 8 years ago

nikisalli

8 years ago

I like how you got rid of the spikes with a sample and hold thingy. Well done

eekee

8 years ago

Thanks :)

hurz

8 years ago

Just leave you with it, I dont like the linearity which is exactly 19.53mV per step http://everycircuit.com/circuit/5300171352309760 but the staicase does not look equidistand

eekee

8 years ago

@hurz Oh goodness! Looks like 2:1 variation in step size between 100mV & 200mV. I'll try to look at that tomorrow.

eekee

8 years ago

Variation also occurs without filter. It's every other step. Hmm... Got it! The ground resistor should be 2R. Fixed!

hurz

8 years ago

Right, now its smooth http://everycircuit.com/circuit/6016375670964224

eekee

8 years ago

I don't know how I didn't see that in the 4-bit (private) version.

hurz

8 years ago

Hmmm

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