Still doesn't explain how the op-amp/comparator knows whether or not it's working off of a dual-supply or single-supply with only two power pins!
I guess you could use a zener diode regulating from the high-side to get a comparator to output a low that is always a certain voltage below the high-side power rail. But I don't think that is how it is done.
Still doesn't explain how the op-amp/comparator knows whether or not it's working off of a dual-supply or single-supply with only two power pins!
I guess you could use a zener diode regulating from the high-side to get a comparator to output a low that is always a certain voltage below the high-side power rail. But I don't think that is how it is done.
MAX912 has +V, -V, and GND pins.
Any op amp with only 2 power pins can work with either dual or single supplies. You just have to obey the common mode input voltage range. The output will limit at the rail voltages, minus whatever internal saturation it incurs. You must have seen this sticky, right?
The output of a (single-ended) operational amplifier is referred to the reference voltage of the circuit, that is the common ground point if you use a dual supply.
Still doesn't explain how the op-amp/comparator knows whether or not it's working off of a dual-supply or single-supply with only two power pins!
I guess you could use a zener diode regulating from the high-side to get a comparator to output a low that is always a certain voltage below the high-side power rail. But I don't think that is how it is done.
That's an op amp isn't it? Don't dual-supply op-amps wired as comparators saturate at the negative rails for a LO output and at the positive rails for a HI output? The MAX912 (comparator) always outputs a ~1V LO and a 3V high regardless of the bipolar or unipolar operation.
Yes, but some comparators (like the LM311) that can operate from a dual supply have a GND pin and their output stage, basically an open collector transistor, can be connected to 0 V. So, the low level will be about 0 V.
Hope this makes sense.
I know. But the op-amps thta have me mystified are the ones that only have two power pins (not 3, it's fairly obvious how those work). The MAX913 for example.