Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2001-Nov-12
A single LED is shown here configurable for any of several dual purpose applications. Traditionally, an LED or an LED array is used only as an optical transmission device. All of the following applications are a result of the ability of the LED to perform bidirectionally. It can convert photons to electrical current as well as its intended mode of light pro- duction. The test circuitry used for light detection is straightforward as depicted in figure 1. The LED drives an OP AMP in a current to voltage mode. Then an OP AMP is used as a voltage gain stage. Table #1 shows the circuit output voltage obtained while the LED was exposed to three different ambient lighting conditions.