[Laser] General comments.

[John Schnurer]

	In general to use a modern laser diode properly:

	A)	Heavy Heat sinking .... more than 2 by 4 inches by 0.25
inches per each 5 mw.  Many system ALSO use Peltier  Effect cooler... and
IT TOO has to be even MORE heavily heat sinked...WITH a fan on the "HOT"
side.

	B)	CURRENT REGULATION
	In general if the diode calls for 1 amp the regulation should be
specified for at LEAST 5 time... better, MUCH better, 10 times this
figure.

	You CAN do this with LM78xx series or LM117 or 317 type
regulators.

	Begin with Voltage rgulator, Adjustable ....and FOLLOW this with
CURRENT regulator.   HEAVY heatsinking on Regulators is VITAL.
	READ the application notes from National Semiconductor, for
example.
	For the Current Regulator, the RESISTOR used MUST be at least 4 to
10 times the magnitude of the designed current output for stability.

	C)

	If you want to MODULATE then put the modulation pass element, ie.,
20 amp IGBT, AFTER all the regulators.   IT TOO must be heat sinked.

	D)	MOST modern diodes hae 3 pins.  CHECK specs for pin out.

	(1)

    One will be a pin common to POWER LASER DIODE and to a Photo diode

	in the package for regulation purposes.
	Acquire and READ manufacturers' spec and application notes. 
	
	(2)
	One will be output FROM photo diode...intended to servo the output
	There are ICs and discrete circuits BOTH, and hybrids, for this
type of drive.


	(3)

	One will be power INPUT ...TO the laser diode element.


	Become familiar..... run a dummy load first if the diode is
important to you.