# 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.

## 2 Answers

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: • This is exactly what I was looking for. Funny, that more than half a century ago this method was unusual: B. D. Smith, "An Unusual Electronic Analog-Digital Conversion Method," IRE Transactions on Instrumentation, June 1956, pp. 155-160. – Roman Susi Jul 31 '13 at 12:34

This is exactly what the low bits of a A/D provide. For example, if you have a 12 bit A/D with a 5 V reference, then the low 8 bits of the result will give you the input voltage modulo 313 mV.

You say you want something simpler than a A/D, but that means you apparently don't know how simple these things are. Everything else I can imagine would either require some sort of partial A/D conversion inside, or have a bunch of level shifters and comparators and the like. A A/D is a single-chip solution that gets you what you want directly. Much of the time a A/D will be even simpler because it is built into a microcontroller you are using for other reasons anyway. The added complexity is wiring the analog signal input a particular pin and a little firmware.

• Thank you. This is a valid answer too, but the idea was to do it in analog domain. I can even imagine, that it's cheaper to chain ADC and DAC, than to implement an ADC stage. – Roman Susi Jul 31 '13 at 12:40