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40kHz Laser Burst Detector - This circuit was originally
designed to detect weak flashed of laser light bounced off of a fabric
video projection screen. It was used as part of a firearm training
system. It generates a 100mS output pulse whenever it detects a 3ms to
5ms-laser burst, modulated at 40KHz. It is very sensitive and could be
modified for long-range laser communications.... [Designed by David A.
Johnson] |
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40kHz Light Receiver Is Immune to Ambient Light - If you want
even more sensitivity than the above circuit, try this design. When used
with a one-centimeter square photodiode, you can achieve a range of
several hundred feet with a standard TV or VCR remote control module....
[Designed by David A. Johnson] |
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40kHz Modulated Light Detector - This circuit uses a unique
cascode amplifier circuit to convert the current from a PIN photo diode
to a current without any feedback network. It is very stable and very
sensitive. The circuit shown has the potential for a conversion factor
of 10 volts per microwatt at 900nm. I included a simple JFET
post-amplifier with a gain of about 20.... [Designed by David A.
Johnson] |
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A 4- to 20-mA loop needs no external power source - 09/13/01
EDN-Design Ideas The simple circuit in Figure 1 uses a
low-current-drain MAX4073H amplifier to sense the current flowing
through a 4- to 20-mA loop. The circuit senses the current through a 1Ω
resistor with a fixed gain of 100 and uses no battery or dc power
supply.... [Design Idea by Shyam Tiwari, Sensors Private Ltd, Gwalior,
India] |
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Air Transparency Monitor, pg 1 - I designed this circuit many
years ago to monitor the quality of a mile long column of air for future
optical communications experiments. The transmitter system (circuit 72
below) uses a powerful xenon flash in conjunction with a large 12 inch
Fresnel lens at the transmitter end and a matching 12-inch lens with a
PIN photo diode at the receiver. The receiver system was connected to a
weather station and a computer to collect the changes in intensity of
the light flashes under different weather conditions. It has the
potential for a 30+-mile range. I have also used this system to conduct
cloud bounce experiments.... [Designed by David A. Johnson] |
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Air Transparency Monitor, pg 2 - This is Page 2 of the air
transparency monitor receiver circuit.... [Designed by David A. Johnson] |
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AN-1244: Photo-Diode Current-To-Voltage Converters - National
Semiconductor Application Note (app note) |
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AN-240: Wide-Range Current-To-Frequency Converters - National
Semiconductor Application Note (app note) |
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AN-772: A Design & Manufacturing Guide for the Lead Frame Chip Scale
Package - AN-772 Analog Devices Application Notes (app
note) |
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Audio equalizer features transimpedance Q enhancement topology -
6-Mar-08 Issue of EDN A novel op-amp configuration enables a
graphic equalizer with a minimal number of amplifiers.... [Design Idea
by Herminio Martínez, Encarna García, and Eva Vidal, Technical
University of Catalonia, Barcelona, Spain] |
SINGLE IC FORMS SENSITIVE MODULATED LIGHT RECEIVER (4069rvr1)
The circuit uses a very inexpensive C-MOS IC that is connected
to a small photodiode. Using a unique inductive feedback
network, the circuit provides high sensitivity under high
ambient light conditions. It is a great circuit when you want to
extend the range of an optical remote control transmitter. |
40KHz LIGHT RECEIVER IS IMMUNE TO AMBIENT LIGHT (40krvr1)
If you want even more sensitivity than the above circuit, try
this design. When used with a one-centimeter square photodiode,
you can achieve a range of several hundred feet with a standard
TV or VCR remote control module. |
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1uS LIGHT PULSE RECEIVER PLUS POST AMP (500krvr3)
This circuit is designed to detect very weak light pulses
lasting 1uS. It uses a tuned LC feedback network to provide high
sensitivity while giving high ambient light immunity. A post
voltage amplifier is included with a gain of about X20. The
circuit is described in more detail in the receiver section of
my
Handbook of Optical Through the Air Communications. Note:
The LF357 op amp is no longer available, this circuit is for
reference only. |
BROAD BAND 5MHz OPTICAL FIBER RECEIVER (5mhzfbvr)
This circuit is a simple broad band light detector that uses a
very inexpensive IC and a PIN photodiode that is packaged for
use with plastic optical fibers. It has a bandwidth from 1KHz to
over 5MHz. It is great for experimenting with various modulated
light sources. |
BROAD BAND 2MHz OPTICAL FIBER RECEIVER (2mhzrvr1)
If you need more sensitivity than the above circuit this circuit
provides about ten times more gain. It too is designed around an
inexpensive plastic optical fiber detector. |
LIGHT RECEIVER WORKS FROM 1KHz TO OVER 70MHz (75mfbvr)
This circuit uses one tiny C-MOS inverter IC to form a modulated
light receiver with a very fast response. It is designed around
a PIN photo diode that is packaged for use with plastic optical
fibers. It can be used as an optical fiber receiver. By using
the open end of the optical fiber it can "sniff" out any
modulated light signals. |
40KHz MODULATED LIGHT DETECTOR (40krvr2)
This circuit uses a unique cascode amplifier circuit to convert
the current from a PIN photo diode to a current without any
feedback network. It is very stable and very sensitive. The
circuit shown has the potential for a conversion factor of 10
volts per microwatt at 900nm. I included a simple JFET
post-amplifier with a gain of about 20. |
40KHz LASER BURST DETECTOR (40krvr3)
This circuit was originally designed to detect weak flashed of
laser light bounced off of a fabric video projection screen. It
was used as part of a firearm training system. It generates a
100mS output pulse whenever it detects a 3ms to 5ms-laser burst,
modulated at 40KHz. It is very sensitive and could be modified
for long-range laser communications. |
10MHz TO 20MHz LASER LIGHT DETECTOR (20mrvr2)
This circuit was originally designed to detect laser light
pulses for an optical Ethernet communications system. It has
good ambient light immunity. |
FET INPUT HIGH SPEED LIGHT DETECTOR (fetamp0)
This circuit is yet another design that converts current from a
PIN photo diode to a voltage. It has a bandwidth that extends
beyond 50MHz. |
AIR TRANSPARENCY MONITOR, XENON FLASH RECEIVER (airmon0)
I designed this circuit many years ago to monitor the quality of
a mile long column of air for future optical communications
experiments. The transmitter system (circuit 72 below) uses a
powerful xenon flash in conjunction with a large 12 inch Fresnel
lens at the transmitter end and a matching 12-inch lens with a
PIN photo diode at the receiver. The receiver system was
connected to a weather station and a computer to collect the
changes in intensity of the light flashes under different
weather conditions. It has the potential for a 30+-mile range. I
have also used this system to conduct cloud bounce experiments.
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LASER/LED LIGHT OUTPUT INTENSITY METER (laserpwr)
This circuit uses a large 1cm X 1cm silicon PIN photo diode and
a transimpedance amplifier to measure the light power output of
infrared and visible LEDs and laser diodes. It can be modified
to produce almost any milliwatts to volts scale factor. It can
be connected to either a multi-meter or an oscilloscope.
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OPTICAL RFID TEST CIRCUIT (opiddemo)
I designed this test the concept of using light techniques to
send identification data instead of RF. A more detailed
discussion on this scheme can be found in the Imagineered new
products section. |
CASCODE LIGHT RECEIVER CIRCUIT (40krvr3a)
This page provides a detailed explanation of how the modified
cascode light receiver circuit operates. The cascode technique
in conjunction with an inductive load provides very high current
to voltage conversion as well as very high speed.
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