This is an 0-24 VDC Ideal Spectroscopy photodiode variable bias module with included 24V, 2A DC power supply. This module is used to apply a DC bias to a compatible photodiode for greater sensitivity and linearity, and more rapid time response. The bias voltage is adjusted via a rotatable knob on the side of the bias module. The photodiode must be attached via the input female BNC connector. The output is monitored by connection to the output female BNC connector. Optionally, the 0-24 VDC bias voltage may be monitored via connection to the bias monitor female BNC connector for precise voltage control.

Photodiodes are light detectors used in many spectroscopy applications. An unbiased photodiode acts as a photovoltaic device, which generates a single electron of current per excitation event. The photodiode output may be monitored either by measuring the current produced or by applying a resistance to the photodiode output and measuring the voltage build up as current is impeded. Photovoltaic operation is the simplest mode of action and has minimal dark current. Unfortunately it suffers from low amplification, nonlinear voltage response over large dynamic ranges, and slow response due to a short depetion width and large junction capacitance. Unbiased photodiodes are best for slow or very low light applications.

Photodiodes may be reverse biased to change their response from photovoltaic to photoconductive. Under reverse biasing the depletion width increases, the junction capacitance decreases, and the response speeds up. The current response is amplified and becomes more linear over a larger dynamic range than in photovoltaic mode. The cost of these enhancements is increased dark noise and the propagation of electrical artifacts from the biasing power supply to the photodiode output signal. Using a clean power supply, such as Ideal Spectroscopy's photodiode bias module, is critical for good response. Biasing photodiodes is best for applications where rapid time response or high linearity over a large range of light intensities is needed.

Photodiode Variable Bias Module Specifications:

• Compatible Photodiodes: Anode-grounded, photoconductive
• Input Voltage: 24 VDC nominal, regulated, <100 mV ripple preferred
• Input Connection Type: Barrel Receptical, 5.5 mm OD, 2.1 mm ID
• Photodiode Bias Voltage: 0.8 - 23.4 VDC, variable
• Photodiode Bias Maximum Current: 3 A, <100 mA typical
• Photodiode Bias Load Regulation: ±2% typical
• Photodiode Bias Line Regulation: ±1% typical
• Photodiode Bias Ripple: <50 mV peak-peak at typical load
• Photodiode Bias Connection: BNC female, center positive
• Bias Monitor Voltage: 0.8 - 23.4 VDC, variable
• Bias Monitor Connection: BNC female
• Output Voltage: 0 - 5 V typical
• Output Connection: BNCfFemale
• Operating Temperatures: -40 to 85 °C
• Operating Humidity: <85% RH non-condensing

24V DC Power Supply Specifications:

• Input Voltage: 90 - 240 VAC
• Input Frequency: 47-63 Hz
• Output Voltage: 24.0±1.2 VDC
• Output Voltage Ripple: ±1%
• Rated Output Current: 2.5 A
• Input Connector: NEMA 1-15P
• Output Connector: Barrel, 5.5 mm OD, 2.1 mm ID
• Output Connector Polarity: Center positive
• Safety Approvals: UL60950-1, cUL60950-1
• EMC Approvals: FCC