>
>In message <19981115133322.AAB2436@[209.239.238.94]>, Rich Measures
><measures@vc.net> writes
>
>snip
>
>>? Bipolar transistors have a secondary-breakdown problem which makes
>>them problematic in HV pass regulator service. Power FETs are virtually
>>immune to secondary-breakdown. . From my experiences, National
>>Semiconductor's 723-based "positive floating regulator" circuit (using
>>FET pass transistors) is good for regulating screen potentials. 2000v
>>regulated output is practical with 600v-rated FET pass transistors.
>>Since FETs operate with zero gate current, paralleling FETs for more
>>current is easy.
>
>Only if they have the same, or fairly similar gate threshold voltages -
>not a problem with same types having same date codes but beware of
>mixing date codes or type numbers without measuring first.
This is why I use an equalizing resistor in the series-pass reg. circuit
on my Web site. FETs should not be paralleled without equalizing
resistors.
>
- later, Steve
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|