Seven Steps To Successful Ultralow Light Signal Conversion

The photodiode remains the basic choice for photo detection among solid-state detectors (Figure 1). It is widely used in optical communication and medical diagnosis. Other applications include color measurement, information processing, barcodes, camera exposure control, e-beam edge detection, faxes, laser alignment, aircraft landing aids, and missile guidance. The energy transmitted by light to one of these sensors generates a current that is further processed using a high precision preamplifier. Analog-to-digital conversion and digital signal processing form the rest of a complete signal chain. The process of selecting a sensor and designing an analog front end can be reduced to seven steps: 1. Describe the signal to be measured and the design goals. 2. Select the right sensor and describe its electrical output. 3. Determine the maximum gain you can take. 4. Identify an optimal amplifier for the preamplifier stage. 5. Design the complete sensor and preamplifier gain block. 6. Run a simulation. 7. Take extra care when building hardware and validate