Aim: To draw the I-V characteristics of the given photodiode (PD) and determine power responsivity of the Photodiode.
Apparatus: Photodiode experimental setup consisting of 0-3V regulated power supply, 0-2mA digital dc current meter, 0-20V digital dc volt meter, white light LED module and photo diode LED type, etc.
Formula : (i) The power responsivity of the photodiode, R_=I_PD/P_LED A/W
(ii) Actual power responsivity of the photodiode =R_/(0.66) A/W
where, IPD is photo current (A) and
PLED is power of LED (W)
Procedure:
Circuit connections are made as shown in the Circuit diagram.
Study of I-V characteristics of Photodiode
The LED (white light) and PD are placed face to face as shown in Figure, and the light arrangement is switched on. LED power is set to 10mW by positioning the knob to its minimum position and VPD is set to -0.1 V and the corresponding IPD is noted. The trial is repeated by increasing VPD in suitable steps up to a maximum of -2V. The experiment is repeated by increasing the LED power to 20mw, 30mw in steps. In each case variation in VPD and corresponding IPD are noted. A graph is drawn for VPD v/s IPD (graph-1).
Determination of Power Responsivity (Rλ)
In this part of the experiment, voltage across the PD is set to -1 V and the PD current IPD is recorded for different LED input power. The LED power is set to 10mw by turning the knob to its minimum position and the PD current IPD is noted. The LED power is increased to 11mw and VPD is again set to -1V and the corresponding IPD is noted. The trial is repeated by varying the input power to 12 mw, 13mw ……. 50mw. In each case VPD is set to -1V and IPD is noted. A graph is drawn for IPD versus PLED (graph-2). Then find the slope of straight line, it gives the Power Responsivity (Rλ) of Photodiode.