D Platt wrote:
> most H's I read about used a combination
> of PNP and NPN. Just wondering why this mixing of xsters is used
> instead of simply using one variant or the other.

PNPs can be more convenient for the high side drive because the base sources
current instead of sinking it.  With NPN high side drivers, the base voltage
needs to be a little above the collector, and requires current coming in.
That can be difficult to arrange when the collector is already tied to the
highest available supply voltage.

This is not to say that using NPNs is "wrong" for high side drivers, just
that the extra difficulties need to be taken into consideration, especially
if you want good efficiency.


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