I have a circuit fed by a 5V source which receives audio signals, amplifies them, and modulates an LED so the intensity of the LED changes with the voltage.
Ok so far so good. But what I want to do is to replace the LED with a laser diode. I tried and it behaves as LED.
In many websites I came across they are using a capacitor and diode when connecting a laser diode. Should I connect a laser diode in a different way than an LED? Why?
In simplest term no, you dont need to handle it differently
but
Laser diodes are usually much more sensitive than regular LEDs. Due to this you will usually see them driven by circuits with capacitors for voltage filtering/smoothing, signal diodes for polarity protection and some form of current limiting, either via a simple resistor or some other means.
So your diode might work but be aware that it might have a low life expectancy.
Resources:
http://laserpointerforums.com/f42/diy-homemade-laser-diode-driver-26339.html
All LEDs are Intensity proportional to current after the threshold current. THe ESR of the operating point is very low in power LEDs is about .5 Ohm per 1 watt device. or 5 ohm per 100 mW, so keep that into consideration with output driver impedance if using a voltage controlled current source such as one of the above suggested schematics.
