[Laser] Mod Power to several lasers?

[Richard Burrows]

Hi

Thanks to you all for the  ideas, I'm going to try them all before #I repeat
the experiment. I thought I was being too optimistic :)
I did get up to four diodes working but when I increased the current to get
others to lase the first four had had enough and gave up and turned into dim
leds.

Anyway thanks again, I will report progress - if there is any.....

                         Richard  G8BYI
----- Original Message ----- 
From: <G0MRF@aol.com>
To: <laser@mailman.qth.net>
Sent: Sunday, August 31, 2003 12:28 AM
Subject: Re: [Laser] Mod Power to several lasers?


> In a message dated 8/30/03 5:37:59 PM GMT Daylight Time,
> r.burrows@blueyonder.co.uk writes:
>
> > I wonder if anyone has an idea how to run six 5mw lasers from a circuit
> > similar to K3PGP's Tx modulator. I can get one diode running fine but
then as
> > you add more diodes the current is shared unequaly between the diodes
(they
> > take what they need)and then they blow!!!!!
> > I could build a seperate K3PGP's Tx modulator for each diode and run
them in
> > parallel, but driven from common mod source, but that  seems over
> > complicated.
> > Has anyone any ideas or circuits they could point me to please.
> >
> >
>
> No problem.......
>
> How about taking seperate dropper resistors from the main supply to each
of
> the laser diodes. These resistors can be individually selected to match
the
> laser diode it feeds. It's the dropper resistor that is really critical in
the
> K3PGP circuit.  The shunt modulator FET or darlington can then be wired
across
> each of the lasers with a normal 1N4001 etc in series with each one to
prevent
> coupling. The silicon diodes will not have any serious effect on
performance
> because although they will have 0.7V across each one, this is  well below
the
> lasing threshold of the laser diodes.
>
> 73
>
> David  G0MRF
>
>
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