Thursday, 15 May 2014

Is there a device to get modulo of voltage value?


This may sound very naive and impractical question, and most likely the answer is negative, but still: is there any more or less simple (simpler than ADC/DAC) analog component or circuit, which makes modulo operation on the value of voltage, given Vref?


For example, if Vref = 1V and input V = 11.56V, then the device will produce 0.56V. Similarly, with Vref=2V, the same input will give 1.56V. Of course, Vinput must be from some sensible range.


If such a thing exists, then it can be used to make a new(?) type of ADC.


UPDATE: I am aware, that modulo function (applied to time) is just a sawtooth http://en.wikipedia.org/wiki/Sawtooth_wave , so there may be some solution involving linearly turning voltage to time period, then reading the sawtooth value.



Answer



Such circuits are already part of many existing ADCs, so if your main goal is just to make a new type of ADC, you might be disappointed.


For an example, see this Analog Devices article about the architecture of a folding ADC. On page 2, it shows a single stage resulting in a 1-bit digitization and a residue voltage, which is the same as the modulo of the voltage. It is only modulo \$V_{ref}/2\$, but by cascading \$n\$ stages you can get the residue modulo \$V_{ref}/2^n\$. The schematic from the article:



single stage




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