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Modulate a current up to 100MHz

Discussion in 'Electronic Basics' started by Opps, Apr 26, 2004.

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  1. Opps

    Opps Guest

    Hi, I am using the following basic and simple circuit to bias a sine
    signal:

    R3
    +/\/\/\+ Vcc
    C | +/\/\/\+ GND
    \ R2
    / R1
    \
    _+_ GND

    with C=50pF and R1=50Ohm to match the impedence of the signal generator and
    to avoid the DC reach its output. Well I adjust R2 and R3 for the correct
    bias.

    Now I need to build a current source driven proportionally with this voltage
    signal.
    I have signal up to 150MHz, current up to 350mA and the load is a LED. Which
    transistor can I use? In which configuration? Well.... in which manner can I
    optimize the LED driving considering that their resistence and capacitance
    can limit the bandwidth of the circuit?

    Moreover, well, I have a post in another NG but I take advantage of this
    post to renew here the question.
    For another application I need to convert this sinewave into a squarewave
    (possibily with adjustable duty-cycle). I got some elegant solution as PLL,
    Line receiver, ... but due to my limitation (in general for my rusty
    electronic) and in particular about the tools I have available, I prefer
    some simpler solution. I think a trigger-schmitt with two transistor can be
    enough. Any suggestion also regarding this subject? I need packages non-SMD
    that I can manage with my low-tech soldering tool :) I will try also with a
    74ALS04 to make a trigger I need... bit I am open to other
    solution/suggestions....

    Thanks,

    Ale
     
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