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C30921E Schematic ( PDF Datasheet ) - PerkinElmer Optoelectronics

Teilenummer C30921E
Beschreibung (C309xxx) Silicon Avalanche Photodiodes
Hersteller PerkinElmer Optoelectronics
Logo PerkinElmer Optoelectronics Logo 




Gesamt 7 Seiten
C30921E Datasheet, Funktion
Description
Silicon Avalanche Photodiodes
PerkinElmer Type C30902E avalanche
photodiode utilizes a silicon detector chip
fabricated with a double-diffused "reach-
through" structure. This structure provides
high responsivity between 400 and 1000 nm
as well as extremely fast rise and fall times
at all wavelengths. Because the fall time
characteristics have no "tail”, the
responsivity of the device is independent of
modulation frequency up to about 800 MHz.
The detector chip is hermetically-sealed
behind a flat glass window in a modified TO-
18 package. The useful diameter of the
photosensitive surface is 0.5 mm.
PerkinElmer Type C30921E utilizes the
same silicon detector chip as the C30902E,
but in a package containing a lightpipe
which allows efficient coupling of light to the
detector from either a focussed spot or an
optical fiber up to 0.25 mm in diameter. The
internal end of the lightpipe is close enough
to the detector surface to allow all of the
illumination exiting the lightpipe to fall within
the active-area of the detector. The
hermetically-sealed TO-18 package allows
fibers to be epoxied to the end of the
lightpipe to minimize signal losses without
fear of endangering detector stability.
C30902E, C30902S, C30921E, C30921S
High Speed Solid State Detectors for
Fiber Optic and Very Low Light-Level Applications
Features
• High Quantum Efficiency 77% Typical at 830 nm
• C30902S and C30921S in Geiger Mode:
Single-Photon Detection Probability to 50%
Low Dark-Count Rate at 5% Detection Probability - Typically
15,000/second at +22°C
350/second at -25°C
Count Rates to 2 x 106/second
• Hermetically Sealed Package
• Low Noise at Room Temperature
C30902E, C30921E - 2.3 x 10-13 A/Hz1/2
C30902S, C30921S - 1.1 x 10-13 A/Hz1/2
• High Responsivity - Internal Avalanche Gains in Excess of 150
• Spectral Response Range - (10% Points) 400 to 1000 nm
• Time Response - Typically 0.5 ns
• Wide Operating Temperature Range - -40°C to +70°C
The C30902E and C309021E are designed
for a wide variety of uses including optical
communications at data rates to 1
GBit/second, laser range-finding, and any
other applications requiring high speed
and/or high responsivity.
EVERYTHING
IN A
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LIGHT.






C30921E Datasheet, Funktion
Appendix
Operation of the C30902S and C30921S
in the Geiger Mode
Introduction
When biased above the breakdown voltage, an avalanche
photodiode will normally conduct a large current. However,
if the current is such that the current is limited to less than
a particular value (about 50 µA for these diodes), the
current is unstable and can switch off by itself. The
explanation of this behavior is that the number of carriers in
the avalanche region at any one time is small and
fluctuating wildly. If the number happens to fluctuate to
zero, the current must stop. It subsequently remains off
until the avalanche pulse is retriggered by a bulk- or photo-
generated carrier.
The C30902S and C30921S are selected to have small
bulk-generated dark-current. This makes them suitable for
low-noise operation below VBR or of photon-counting
above VBR in the Geiger mode. In this so-called Geiger
mode, a single photoelectron (or thermally-generated
electron) may trigger an avalanche pulse which discharges
the photodiode from its reverse voltage VR to a voltage
slightly below VBR. The probability of this avalanche
occurring is shown in Figure 8 as the "Photoelectron
Detection Probability" and as can be seen, it increases with
reverse voltage VR. For a given value of VR-VBR, the
Photoelectron Detection Probability is independent of
temperature. To determine the Photon Detection
Probability, it is necessary to multiply the Photoelectron
Detection Probability by the Quantum Efficiency, which is
shown in Figure 2, the Quantum Efficiency also is relatively
independent of temperature, except near the 100 nm cutoff.
The C30902S and C30921S can be used in the Geiger
mode using either "passive" or "active" pulse quenching
circuits. The advantages and disadvantages of each are
discussed below.
Passive-Quenching Circuit
The simplest, and in many cases a perfectly adequate method
of quenching a breakdown pulse, is through the use of a
current limiting load resistor. An example of such a "passive"
quenching circuit is shown in Figure 9. The load-line of the
circuit is shown in Figure 10. To be in the conducting state at
VBR two conditions must be met:
1. The avalanche must have been triggered by either a
photoelectron or a bulk-generated electron entering the
avalanche region of the diode. (Note: holes are inefficient at
starting avalanches in silicon.) The probability of an avalanche
being initiated is discussed above.
2. To continue to be in the conducting state a sufficiently large
current, called the latching current ILATCH, must be passing
through the device so that there is always an electron or hole in
the avalanche region. Typically in the C30902S and C30921S,
ILATCH =50 µA. For currents (VB-VBR)/RL, much greater than
ILATCH, the diode remains conducting. If the current (VR-
VBR)/RL, is much less than ILATCH, the diode switches almost
immediately to the non-conducting state. If (VB-VBR)/RL, is
approximately equal to ILATCH, then the diode will switch at an
arbitrary time from the conducting to the non-conducting state
depending on when the number of electrons and holes in the
avalanche region statistically fluctuates to zero.
When RL is large, the photodiode is normally nonconducting,
and the operating point is at VR - IdsRL in the non-conducting
state. Following an avalanche breakdown, the device recharges
to the voltage VR - IdsRL with the time constant CRL where C
is the total device capacitance including stray capacitance.
Using C = 1.6 pF and RL = 200.2 Ka recharge time constant
of 0.32 microseconds is calculated, in reasonable agreement
with observation as shown in Figure 9. As is also evident from
Figure 9, the rise-time is fast, 5 to 50 ns, decreases as VR-
VBR increases, and is very dependent on the capacitances of
the load resistors, leads, etc. The jitter at the half-voltage point
is typically the same order of magnitude as the rise-time. For
timing purposes where it is important to have minimum jitter,
the lowest possible threshold of the rising pulse should be
used.

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