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LED Driver for OFDM signal

Syifaul Fu75
Prodigy 10 points
Other Parts Discussed in Thread: OPA842, OPA333

Hi everyone,

I am looking to design an analogue modulator with a bandwidth of over 10MHz for OFDM signal transmitted by LED. I try to transmit sinusoidal signal which is generated by function generator to prove my design. Based on experiment, by using common emitter we get square output from sinusoidal input signal.

Then, I am not so sure wether a Push pull configuration or current sink is the best option.
Can anyone help with the correct design? also suitable components (such as OP-AMP, BJT, MOSFET) please.
I attached the figure of my electronic circuit below

Thank you.

  • TI__Genius 12631 points

    Your 1st circuit with the opamp circuit - that is positive feedback. Also, I am unclear how you expect the circuit to work.

    Your 2nd circuit is open-loop...may not be the most optimum stable solution.

    Here is a potential closed-loop opamp solution. For the amplifiers you could use the OPA842 instead of the OPA333 for higher speed. TI doesn't have a very wide choice for the MOSFETs you are seeking. You could look for it on Digikey. You should select the MOSFET based on the required speed and the amount of current drive the LED requires.