Photodiode Circuit
From Physics 111-Lab Wiki
All pages in this lab
I. Nonlinear Spectroscopy and Magneto-Optics
II. LabView Program Descriptions
III. Photodiode Circuit and Data Sheet
IV. Tuning the Laser
Photodiode circuit
In this lab, we use several silicon photodiodes to measure the intensity of laser beams and of atomic fluorescence light. The simple circuitry that we use (the photodiode bias and load resistor box) is shown in Figure A2. Here, the photodiode operates in the photoconductive mode in which a reverse bias is applied to the diode and no current is flowing through the circuit in the absence of light (neglecting the dark current, which actually becomes important in small-signal applications). In the absence of current, there is also no output voltage across the load resistor. When a photon strikes the photodiode, it creates an electron-hole pair in the conductivity band in the carrier-depleted zone of the photodiode's pn-junction. The quantum efficiency of this process may reach nearly 100 %, meaning that there is one pair produced per incident photon. The charges then flow through the load resistor upon the action of the bias voltage, thus producing output voltage.
