[time-nuts] PIN diode shunt clamp

Brooke Clarke brooke at pacific.net
Wed Apr 2 12:57:47 EDT 2008

Hi Shane:

No.  It's a long lifetime PIN.  Limiter PINs must have a lifetime short enough 
that they have some retification efficiency.

See attached schematic.

Have Fun,

Brooke Clarke
http://www.prc68.com/P/Prod.html  Products I make and sell
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Shane wrote:
> I'm a little curious about the limiter mentioned below.  
> In laymen's terms would this be pairing a schottky diode and limiter PIN in
> series or parallel?  
> I've seen designs with different pins (course and fine) in parallel to act
> as clean ups.  
> If you use DC blocks and no DC return... Could you effectively forward bias
> the PIN in parallel by rectifying a reverse polarity schottky with the
> proceeding negative AC cycle?
> Sorry if it's a silly question, I need to review some elementary circuit
> stuff.
> -----------------------
> 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.
> 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
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