Laser diode driving circuit having a temperature compensation circuit

A laser diode driving circuit capable of compensating for changes in temperature, comprising:

• 1) a first circuit including a transistor connected in series with a laser diode for driving said diode, said transistor supplying a forward current to said diode;
• 2) a second circuit connected in parallel to said first circuit, said second circuit including:
• a) a first variable resistor,
• b) a FET connected in series with said first variable resistor,
• c) a second variable resistor connected in series with said FET and first variable resistor, and
• d) a node between said first variable resistor and said FET being connected to a base of said transistor of said first circuit;
• and
• 3) said FET and said second variable resistor of said second circuit constituting a constant current circuit which varies an output current in response to changes in voltage at the base of said transistor caused by temperature fluctuations, whereby said first variable resistor converts said output current into a voltage applied to the base of said transistor so as to maintain an output of said laser diode constant relative to changes in temperature.