Can I convert a +-6V square wave to a 0 to +12 one (at audio rates) without adding a bypass capacitor?A 10uF capacitor kind of messes (skews) the waveform at low Hz rates so ideally I would like to try and avoiding it.I thought about using a comparator with an opamp's VEE pin to GND so that would give me a perfect 0 to 12 square but I was wondering if there's an easier more clever shift solution.
4 Answers
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You could use an OpAmp in a "two-input non-inverting adder" configuration with all resistors of the same value and connect the bipolar signal to one input and a constant voltage of 6V to the other input. (see the following figure):
(You can also use a single supply for the OpAmp but the output signal does not go to zero)
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If the inversion isn’t needed, so at +6V on input you will get +12V on output a transistor common base connection can be used:
Red is input, green is output:
Note: The +-6V signal source must allow to sink about 6V/1k5=4mA at least.
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1\$\begingroup\$ Love common-base circuits - unsung heroes. \$\endgroup\$AnalogKid– AnalogKid2025-04-26 14:41:21 +00:00Commented Apr 26 at 14:41
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You can use an op-amp, and if you don't need much current for your output signal, you could use a 12V supply with a rail to rail op-amp, like so:
simulate this circuit – Schematic created using CircuitLab
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Since 1972, many comparators have an input stage with an input common-mode voltage range that includes the device's negative rail. That means that with a device powered by only +12 V and GND, it will perform correctly with an input signal that goes above and below GND. Thus, it can be a very low parts-count zero-crossing detector. Schematic on request.
