Photodiode Transimpedence Amplifiers

The PDA-700 is a low noise, high gain, transimpedance amplifier designed to provide a direct digital readout of the current generated from a photodiode, photomultiplier or other similar current source. Digital selection of a calibration factor in terms of Amp/Watt via the front panel controls permits the unit to display the measurement directly in Watts. The A/W setting may range from 1.0000 to 0.1000. Subsequent current readings are divided by this cal factor when the Amps/Watt control is engaged. A variable bias voltage, ranging from +10V to -10V, may be digitally selected from the front panel and applied in series with the photodiode under test. The background cancellation feature allows offsets from +200% to -200% of the selected full scale range to be added to or subtracted from the input signal.

A large liquid crystal display provides a maximum resolution of 1 part in 20,000, thus permitting the detection of very small changes in the variable that is to be measured. the display is also equipped with an LED back-light for reading in a darkened laboratory. An analog output is provided with a 2 volt full-scale signal that is proportional to the maximum display reading of 20,000 counts. Rechargeable batteries isolate the unit from the mains and eliminate the effects of ground loops and/or power line noise. They provide power to the unit for a minimum of 20 hours of operation between charges. The unit may be operated normally while the batteries are charging. The instrument is covered by a standard two year limited warranty.

Applications include: serving as a readout for Unity Quantum Efficient Detectors such as those manufactured by Graseby Optronics, characterization of detector dark current, spectral calibration of detectors and use as a sensitive low cost optical power meter.

Contact Laser 2000 for further details.

   PDA 700

Features and Advantages:

• 7 decade full scale dynamic range +/-20 nA to 2.0 mA
• Max input without damage: +/-10 mA
• Accuracy: +/-0.5% Rdg +/-2 LSD
• Amps/Watt setting: 0.1000 to 1.0000
• Amps/Watt setting accuracy: +/-0.5% Rdg +/-2 LSD
• Digital input of A/W value provides direct readout in Watts
• Input impedance: 0 Ohms, single ended
• Input capacitance: 25pF
• Output impedance: 100 Ohms
• Bias voltage: -10V to +10V
• Drift: <20pa/hr after 10 minutes warm up period
• Voltage noise: <1.1 uv, dc to 10hz
• Noise: <1 pa with <10 pf det.
• Background cancellation: +/200% of range in use
• Temperature coefficient: <2pa/°C
• Frequency response: DC to 2000Hz
• Display: 4 1/2 digit, 0.4" high LCD with LED back lighting Maximum resolution 1 part in 20,000
• Rechargeable Ni-Cad batteries, 20 hours of use
• External supply: 110 or 240 VAC, 50-60Hz, 15W max
• Dimensions: 16.5cm x 23cm x 7 cm
• Weight: 1.36 Kg (excluding external supply)
• Operating temperature: 0-400°C