DEC H744 +5 supply

Brent Hilpert bhilpert at
Fri Sep 21 19:07:13 CDT 2018

On 2018-Sep-21, at 4:03 PM, Noel Chiappa via cctalk wrote:
>> From: Brent Hilpert
>> If the heatsinks seem huge compared to modern day supplies, that's more
>> likely the result of technology improvements - faster devices, and
>> moving from bipolar switching transistors to mosfets. Bipolar
>> transistors have a near-fixed voltage drop which can't be reduced
> Right, I knew bipolars had the fixed drop, but I hadn't made the connection
> to that being the cause of the large amount of heat needing to be dumped.
> Useful enlightenment!

To clarify, bipolars have a fixed MINIMUM drop, which can be used in a switching supply to as much advantage as possible with bipolars, but have a varying drop in a linear regulator (that's where the 'linear' comes from) which results in the large losses and inefficiency of linear regs.

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