DC voltage processing: having trouble understanding some concepts

[David]

This is a thought experiment or a conceptual problem that I admit I do not have the experience or training to solve.

A certain linear Hall-effect sensor will output a DC voltage that varies between +2.5VDC and 0VDC depending on its proximity to the south pole of a magnet.  This voltage is output at around 5 or 6 ma.  It is a simple matter to vary the brightness of an LED this way.  I found you can connect it directly.  However, with this voltage and amperage available, it is only possible to connect one.  Darn it, that's not enough!

We see audio buffers around here all the time.  I've also seen examples of using op-amps to buffer DC voltage.  Unfortunately, those examples seemed to require dual-polarity power supplies.  I'll have to exclude those from consideration as I only want to mess with a single-polarity supply.  All right, suppose I have an op-amp noninverting buffer.  The sensor above requires 5VDC power, so I could power the op-amp with that, or from a 9VDC wall wart which would power the sensor through a 5V regulator.  The million-dollar question is, is there a way to use a single-polarity powered noninverting op-amp buffer to drive -- let's say 4 LEDs from the sensor's output?

[cpm]

this was for another circuit, but you get the idea... the opamp in the drawing would be your device's output
...may work

[JKowalski]

How about:

Instead of attaching the other end of your hall sensor to ground, attach it to Vcc/2.Then you have an output voltage of Vcc/2 -> Vcc/2 + 2.5V, which is easily buffered without decoupling. The LED's will go from the buffered output to Vcc/2.

If you already have a voltage reference of 5V for your sensor, then why not use that as your Vcc/2? It's fine if it's not centered, in this application.

[David]

That certainly appears to be worth trying.     Thanks!