[time-nuts] PIN diode shunt clamp
time at artemisinc.net
Wed Apr 2 12:27:00 EDT 2008
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
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
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:
More information about the time-nuts