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be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
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page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: Laser Receiver Posted: Fri Aug 11, 2006 6:20
Joined: Fri Aug 11, 2006 6:07 am
I need to design a laser receiver circuit which would receive
laser pulses in the red region of the spectrum (around 630nm wavelegth),
the laser pulses carry an RF ripple of around 315MHz. I built a current
to voltage converter using a transimpedance amplifier with resistor
feedback and simulated it on Multisim, it seems to be working fine.
But I have a couple of problems, firstly, the transimpedance amplifier
is an inverting amplifier so I need to reinvert the signal or get it
straight the first time with minimum distortion. Secondly, I need to
find a way to have two outputs for the device, one giving the equivalent
output voltage of the signal (DC with a 315MHz ripple) and the other
with AC coupling (just the 315MHz ripple). And the last problem is that
I need to make the system as noise-immune as possibe. If anyone can
help me or point me to where I can find something that would help I'd
appreciate it a lot.
Posted: Fri Aug 11, 2006 7:55 am
Fri Feb 17, 2006 12:07 pm
Location: London UK
first reaction is try to separate the dc from the 315MHz components
at as early a stage as possible.
What is the source/spectrum of the
Posted: Fri Aug 11, 2006 8:15 am
Aug 11, 2006 6:07 am
Well, there's no specific source,
it's just thermal noise, shot noise and other regular sources of interference.
I can put two parallel transimpedance amplifiers, one to separate the
RF alone and the other just to convert the signal to voltage as a whole,
but the problem is that I get a weird transient of a relatively low
frequency whenever there's a pulse transition when I try to separate
the RF alone, I guess it's due to the presence of the L and C in the
transimpedance amplifier, I'm still trying to figure out how to remove
Post subject: Posted: Fri Aug
11, 2006 1:14 pm
Joined: Fri Aug 11, 2006 6:07
I think I was able to do it but I just have one more
question left. I'm supposed to add an enable signal to the circuit,
what would be the best way to implement that? Is it through a transistor
that passes Vcc to the whole circuit when it receives the needed signal
or through a transistor that passes the output signal when it receives
the enable signal?
Post subject: Posted:
Fri Aug 11, 2006 1:23 pm
Joined: Mon Jun
27, 2005 2:02 pm
To answer to your last question, I recommend to use the first option,
i.e. to control over the Vcc supply voltage. This will promise a full
isolation and will block any leakage or residual signals to the output.