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I am designing a fast pulse generator, inspired by Leo Bodnar's pulse generator, using the ADCMP572 ultra fast comparator.

Leo Bodnar's fast pulse generator

It looks like a pretty simple device, using a PIC microcontroller to drive the inputs of the comparator. However, for some reason the whole board is powered using a LT1931 voltage inverter. This means that the shields of the coax connectors are sitting at a negative voltage, and the output square wave switches between 0v and -0.7v.

Is there some benefit to using a negative voltage here? Does it help improve the edge quality. Or perhaps it's just a convenient alternative to using a bock/boost regulator to guarantee a 5v potential difference?

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  • \$\begingroup\$ It looks like the designer never intended the product to be used with the power supplied by a grounded USB cable, but rather to be used with a wall wart kind of USB supply. It's hard to tell since he has (quite understandably) declined to provide schematics as far as I can tell. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Feb 20 at 19:11

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