Amplifier: Trans impedance Circuits

SINGLE IC FORMS SENSITIVE MODULATED LIGHT RECEIVER(15) (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 (16) (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.

1uS LIGHT PULSE RECEIVER PLUS POST AMP (27) (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 (30) (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 (31) (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 (48) (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 (59) (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 (60) (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 (61) (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 (69) (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 (70) (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.

LASER/LED LIGHT OUTPUT INTENSITY METER (80) (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.

OPTICAL RFID TEST CIRCUIT (87) (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 (103) (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.