respectively [25]. The composite video signal following amplification and filter is compared with the linear ramp carrier signal at a frequency of 15 MHz, which is only four and five times thefc-sub, using a high-speed comparator (with the propagation delay and rise/fall times of 4.5 and 1.5 ns, respectively).
Figures 4 and 5 show the audio and video transmit-ter modules. The transmission distance between the LEDs and the optical receiver was measured at the point where the video and audio play worked well. Of course, the link span is dependent on the optical transmit power and the photodetector (PD) receiver sensitivity. We have de-signed an LED driver module, which supports a max-imum power of 500 mW. The schematic diagram of the LED driver is shown in Figure 6a. At the first stage, two high speed comparators (TLV3502) with a maximum output current of 74 mA function as a NOT gate with two inverted output signals. The output of the first stage drives the second stage driver where a fast switching power MOSFET (Si1563 from Vishay, Malvern, PA, USA) is used to drive the LED panel. A push-pull configuration is adopted for the second stage in order to supply a max-imum of 500 mW to the LED panel. The circuit diagram and the driver board of the LED driver are shown in Figure 6 b,c, respectively.
respectively [25]. The composite video signal following amplification and filter is compared with the linear ramp carrier signal at a frequency of 15 MHz, which is only four and five times thefc-sub, using a high-speed comparator (with the propagation delay and rise/fall times of 4.5 and 1.5 ns, respectively).
Figures 4 and 5 show the audio and video transmit-ter modules. The transmission distance between the LEDs and the optical receiver was measured at the point where the video and audio play worked well. Of course, the link span is dependent on the optical transmit power and the photodetector (PD) receiver sensitivity. We have de-signed an LED driver module, which supports a max-imum power of 500 mW. The schematic diagram of the LED driver is shown in Figure 6a. At the first stage, two high speed comparators (TLV3502) with a maximum output current of 74 mA function as a NOT gate with two inverted output signals. The output of the first stage drives the second stage driver where a fast switching power MOSFET (Si1563 from Vishay, Malvern, PA, USA) is used to drive the LED panel. A push-pull configuration is adopted for the second stage in order to supply a max-imum of 500 mW to the LED panel. The circuit diagram and the driver board of the LED driver are shown in Figure 6 b,c, respectively.
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