POWER GENERATION DIODES
Step recovery diodes and m ultiplier varactor applications
STEP RECOVERY DIODES AND MULTIP LIER
VARACTOR AP P LICATIONS
A Step Recovery Diode (SRD) generates pulses that can be used to m ultiply frequencies, and to set up
reference points, e.g. for synchronizing test instrum ents.
This device operates by alternately producing and consum ing a charge, based on the frequency of its
input signal. During forward bias, the SRD conducts and builds up its charge. During reverse bias,
the SRD m aintains conduction by consum ing its charge. When the charge has been fully consum ed, the
SRD snaps off, i.e. very quickly reverts to zero conduction.
This device acts as a switch, controlling current flow by alternately storing and releasing its charge, forming
pulses at a repetition rate equal to the frequency of its input.
The output of a step recovery diode is m ost often used in two ways:
•
•
a pulse train can be applied to resonant circuits, which provides output power at a frequency
above that of the original input,
a pulse train can be used to develop a series of frequencies at m ultiples of the original input
frequencies.
Typical applications of step recovery diodes include oscillators, power transm itters and drivers,
for telecom m unications, telem etry, radar and test equipm ent.
In choosing a SRD, the significant characteristics include:
Output Frequency (f ) ; Breakdown Voltage (V ) ; Junction Capacitance (C ) ; Minority Carrier Lifetime (τl);
o
BR
j
Snap-offTim e (t ) ;Therm al Resistance (R ) and Output Power (P ).
so
th
o
Multiplier varactors
A m ultiplier varactor is a physical stack of series-connected SRD units.This configuration is capable of
m ultiplying power.
Power out
Power in
Packages for m ultiplier varactors are designed to dissipate the power yield
(
(
Most of these packages hold from 2 to 4 chips, this type of com ponents are available on custom er
request.
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