[time-nuts] Adding prescaler to HP 5334B

Brooke Clarke brooke at pacific.net
Tue Apr 1 16:36:48 EDT 2008


Hi Bruce:

One way to do that is pair up a long lifetime PIN and a schottky of polarities 
such that the Schottky current forward biases the PIN.  DC block the input and 
output.  I made microwave limiters this way many decades ago.

Re: Schottky Diodes
There are two flavors.  A pure Schottky diode is made up of a single metal 
semiconductor junction.  These typically have reverse breakdown voltages in the 
3 to 5 volt area.  If a "Schottky" diode has a higher Vbr then it's what's 
called a "Guard Ring" type.  These have a P/N junction surrounding the schottky 
junction that increases the reverse breakdown and another P/N junction to 
isolate the two forward curves.  Sometimes these are made improperly where the 
second PN junction gets shorted and then there's a "double break" in the 
forward I-V curve and charge storage (slow operation) is associated with them.

When HP first introduced microwave Schottky diodes they put a reverse recovery 
time spec on them when in fact it was zero.

For more on Microwave Diodes see:
http://www.prc68.com/I/Diodes.html


Have Fun,

Brooke Clarke
http://www.prc68.com/P/Prod.html  Products I make and sell
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Bruce Griffiths wrote:
> Robert Berg wrote:
> 
>>Bruce,
>>
>>Thanks for the ideas. The HSMS-2822 looks like it could serve in the
>>detector role, while a pair of HSMP-3822's might work for clamping--low
>>capacitance, matched pair in series, and in stock at Mouser. The 3822 is
>>actually a pair of PIN switch diodes, but couldn't it function as a clamper?
>>The 482x series looks better for clamping, but isn't available in a
>>series-pair configuration. There are other possibilities, but not many in
>>stock, and I couldn't find any suitable ring diode packages.
>>
>>Bob
>>WA7ZRX
>>
>>  
> 
> Bob
> 
> A PIN diode shunt clamp can be used, however it will take a while to 
> respond so some other means to clamp the unwanted energy during the time 
> it takes to turn on the PIN diode clamp may be necessary.
> 
> Bruce
> 
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