The infrared LEDS fabricated from GaAs or GaAlAs discussed here are PN semiconductor junction diodes fabricated from GaAlAs or GaAs and typically emit at wavelengths in the range 850 - 950 Visible semiconductor lasers found in common laser pointers emit at about 650 +- 20 nm and are commonly in the Class IIIA Laser Product category, emitting less than 5 mW under Mims III, 1984, Radio Shack "Engineer's Mini-Notebook: Op Amp IC Circuits", Forrest M. A peak pulse current of about 900 mA was measured. check over here
The lower trace shows the Si PIN photodiode signal showing a similarly fast optical pulse. Scope display showing collector voltage (blue) and PIN photocurrent at Vcc=10 V Ic = 600 mA. The PDA10A photodetector has a responsivity of 0.25 mA/mW at 870 nm and a transimpedance gain (into 50 ohm) of 5V/mA providing a photodetection sensitivity of 1.3 V/mW. Saw them. read the full info here
The lower blue trace is the laser voltage (6V peak drive value). Powered by vBulletin™Copyright © 2017 vBulletin Solutions, Inc. A x10 attenuation probe was used and the voltage source was 100 VDC. Also, if you have access to simulation, try out your ideas with that first.
Using a current booster high-speed switching output transistor, very high output optical levels are possible. Therefore the power received by the photodiode should be 6.4x10-4 X 1400 or about 0.9 mW. The standard TTL 7404 hex inverter has a switch time on the order of 10 ns. How To Build A Laser Diode Driver Circuit Any suggestion for a schematics?
A simple example of one approach is shown below. Wiring from the 555 to the laser should be short to minimize inductive effects which can cause ringing. Without the LED connected, the electrical pulse across the output 50 ohm resistor is shown below: With the LED connected, and the optical output pulse from an 870 nm high-radiance Vishay The 2N2222a has tr/tf of 20-50 ns but potential charge storage effects can easily cause pulse broadening to hundreds of ns.
The peak emitter and LED voltages during the pulse were 26 and 4.2 V respectively. Isl58837 Giora 28th August 2013,06:20 28th August 2013,07:42 #2 keith1200rs View Forum Posts Private Message View Blog Entries View Articles Super Moderator Achievements: Join Date Oct 2009 Location Yorkshire, UK The infrared LED is modelled as two Si switching diodes in series: It is possible to simplify the avalanche breakdown driver circuit by removing the pulse-shaping inductor, and placing the IR Giora 28th August 2013,09:57 #6 keith1200rs View Forum Posts Private Message View Blog Entries View Articles Super Moderator Achievements: Join Date Oct 2009 Location Yorkshire, UK Posts 10,877 Helped 2073 /
For example, the TSFF5210 high-radiance 870 nm LED is specified with a radiant optical power of 50 mW at 100 mA and over 250 mW at 1Amp drive current. Using a SEP8703-001 880 nm LED (Radio Shack/The Source # 276-143a), the following LED drive current results are achieved: Vcc= 5.0 Ic = 250 mA Vcc=10 V Ic = 600 mA High Speed Laser Driver Circuit The beam is directed to a tilt-mount mirror about 1 meter in the forground (not visible) and reflected back onto the pin photodiode (in forground): To obtain an optical pulse from Pulsed Laser Diode Driver The LED specification sheet claims a radiant intensity of about 1400 mW/sr at 800 mA.
However, high radiance fast LEDs typically have response times on the order of tens of nanoseconds. check my blog The avalanche transistor breakdown pulse source is simulated simply as the capacitor C1 charged initially to 70V (the breakdown voltage). Thanks. This transistor when operated in the avalanche breakdown region, can be used to generate sub-nanosecond pulses for various applications including testing high-speed oscilloscopes. High Power Laser Diode Driver Circuit
Giora 28th August 2013,13:54 #8 keith1200rs View Forum Posts Private Message View Blog Entries View Articles Super Moderator Achievements: Join Date Oct 2009 Location Yorkshire, UK Posts 10,877 Helped 2073 / Many interesting and useful applications can be found in the references cited here, as well as several online web pages. Many such pointers can easily be disassembled and pressed into pulsed service as demonstrated here. this content The output pulse is also more symmetrical than the input pulse: To verify the high emitted optical power from the LED under a drive current of 800 mA, the detector with
A suitable low current 100 VDC power supply can be assembled easily using a 115VAC/25VAC transformer or adapter and a voltage tripler circuit. Pulsed Laser Diode Driver Module In this approach greater collector capacitance is required to achieve high pulse currents and the results will depend more on the specific 2N2369a transistor used. By changing C1 to 100 pF, a somewhat narrower pulse of 25 nS is achieved with a lower peak current of about 600 mA.
A 51 ohm shunt resistor works well as shown in the circuit below: With C1 = 220 pF and Re = 22 ohm, good results were obtained with Motorola 2N2369a transistors. Considerably higher peak power outputs can be achieved if the LEDs are pulsed with short pulses in the range of 1 us to 100 us with low duty cycles of 1 This confirms the high radiant intensity achieved under these conditions. Laser Diode Driver Circuit Design Then, if you have problems at lower voltages you can increase it.
They use a source follower configuration which is quicker but you are limited as to how far you can take that idea by gate-source voltage limitations. A simplified circuit simulation using the component values in the circuit above is shown below. However, the laser must be placed in the collector circuit due to the higher voltage requirement of a visible laser (compared to an infrared LED). have a peek at these guys Also an LED shunt resistor should be used so that the emitter circuit contains a low resistance path during the avalanche breakdown decay.
See Forrest Mims Circuit Scrapbook for a good discussion of this approach. Register Remember Me? At this distance, the peak photodiode signal voltage was measured to be 1.1 V. A feedback shunt capacitor of 5 pF across Rf suppresses gain peaking. (Rf of 1 kohm enables 16 MHz BW with a 10 pF peaking capacitor; Rf of 220 ohm enables
The collector voltage trace below shows the charging and avalanche-breakdown and discharge cycle. One of the fastest solutions for a low voltage would be the Osram SPL LL90_3 as they build the laser/MOSFET and capacitor in a single package but I think that only