Hi, I am designing a visible light communication system. The LED has to be modulated directly with my data signal. I have generated the data signal from a waveform generator (200 MHz frequency). The bipolar signal is biased with some voltage using tee-bias since the LED cannot respond beyond threshold and for negative voltages. But the LED needs a current signal to drive on. So, I need to use a resistor to convert my voltage signal into current.
If a voltage signal is input to bias, and the bias is supplied with say 2 Volt, then the output signal is a voltage signal offset by 2 V.
But, if a resistor/potentiometer is added in the path of dc supply and bias supply port, what type of signal do I expect at output. Is it a current signal that can modulate LED (or) voltage signal with an offset (or) both the same.
i have attached the two possible designs below. Which of these can give an output current signal suitable for my LED.

 

The potentiometer in the second circuit attenuates the carrier wave, as in, "bad".

 

Yes, That is a valid point. But Do you think the first configuration gives a current signal to modulate my LED?