PHOTODIODE AMPLIFIERS: OP AMP SOLUTIONS

Light photons impinging upon a semiconductor material in the vicinity of a P-N junction release conduction carriers to produce current flow through the photodiode effect. Photodiode amplifiers convert this current to a voltage in a relationship that remains linear as long as the amplifier eliminates signal voltage swing from the photodiode. For this purpose, the simple current-to-voltage converter or transimpedance amplifier presents a virtual ground to the diode. However, when connected to a photodiode, this simple op amp circuit displays surprising multidimensional constraints that defy conventional op amp intuition.