### DESCRIPTION

This is an Arduino shield that is designed to drive an LED at 4.2V/800mA max.  It's intensity can be driven across 4-orders of magnitude via a 12-bit DAC, and the LED can be switched from 0% to 100% intensity at >1MHz.

### TECHNICAL DETAILS / COMPONENTS

This circuit used a 12-bit DAC as a reference on a constant current opamp.  The current sense resistor is 4.7 ohms, and the DAC has a 4V output, allowing up to 850mA operation.  The intensity of the LED can then be adjusted via the DAC.  

The MHz modulation is though a SPST analog switch with a 10 ns switch time.  This allows for full scale modulation via a TTL signal to the switch input.  

Since the device is a linear regulator, it can generate up to 10W of heat.  This heat is dumped into a heatsink, and the enclosure ensures ducted airflow over the heat sink.  The board includes a thermistor to both turn on the fan at a set temperature, as well as allowing for a thermal shutoff in the even of overheating. 

### LEARN / TOPIC / BUILD INSTRUCTIONS