In my case, the LM393 ground is my -15v and and the LM393 supply is my +15v. So it pulls down to -15v.
And....yes, I use current steering to drive the Led. Generally speaking I use a lot of LTPs and CCSs.
You actually don't need to run the LM393 on bipolar rails if you are only peak detecting on one polarity, if you need fullwave peak detection then you might justify bipolar power easily. The LM393 can run that LED directly even on bipolar power rails - just a single rather significant value series resistor is required. (Depending on LED 15K - 33K)
Here's another way to drive an LED using a constant current source. Supply current is constant even when the LED blinks twenty thousand times per second.
If you worry about the Vce_sat of the open collector driver transistor, simply install a diode or two between the LED cathode and the negative supply rail. Or a resistor, chosen such that R = (2 volts) / I_ccs .
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If you worry about the Vce_sat of the open collector driver transistor, simply install a diode or two between the LED cathode and the negative supply rail. Or a resistor, chosen such that R = (2 volts) / I_ccs .
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