This is a customized OEM version of Femto's LCA series low noise current amplifiers. These are new old stock and we've individually tested them to verify functionality. Used as a transimpedance amplifier for current sources such as photodiodes and photomultiplier tubes. Datasheet included with each unit. Also marked with LGR (Los Gatos Research?) PN 112-0006-0003. As best I can tell, the customization on these is the addition of a -100mV bias voltage on the input BNC intended for use with Judson Photovoltaic MCT detectors and an external offset compensation input on the power connector. In testing here I found that these work well with PIN photodiodes and it is possible to increase the reverse bias for photodiodes requiring more than 100mV by connecting the cathode to a positive voltage rather than ground. Increasing the reverse bias voltage in this way does not add any appreciable offset at the output. These need a low-noise ±15V DC power source.

We're offering these in 3 configurations - With or without the LEMO power connector or with a pre-wired power supply to get you up an running quickly. Note that these use a 5 conductor LEMO connector which is different from the 3 conductor type used on Femto's standard models. I think the connector is LEMO part number FFA.15.305.CLAC42 for cable diameters up to 4.2mm or the same but ending in CLAC52 for cables up to 5.2mm diameter.

Features

• Transimpedance (Gain) 50 kV/A
• Bandwidth DC - 200 kHz
• Low Equivalent Input Noise Current of 0.8 pA/√Hz
• -100 mV Bias Voltage at Input Center Pin

Applications

• Photodiode Amplifier for MCT - Mercury Cadmium Telluride (HgCdTe) detectors for mid-IR light
• Photovoltaic Detector

Specifications (Test Conditions: Vs±15 V, Ta = 25°C)

• Transimpedance: 50kV/A (@ > 100 kΩ Load)
• Accuracy: ±1%
• Frequency Response
  • Lower Cut-Off Frequency: DC
  • Upper Cut-Off Frequency (-3 dB): 200 kHz (±10%)
  • Max. Source Capacitance: 1 nF (incl. cable, e.g. typical coax cable 1 pF/cm)
  • Rise-/Fall-Time: 1.7 µs (10%-90%)
• Input
  • Equ. Input Noise Current: 0.8 pA/√Hz (@1 kHz)
  • Equ. Input Noise Voltage: 6 nV/√Hz (@1 kHz)
  • Equ. Integrated Noise: 2 nA peak-peak
  • Input Bias Current: 5 pA typ.
  • Input Bias Current Drift: factor 1.7/10 K
  • Offset Current Compensation: ±100 µA, adjustable by offset-trimpot
  • External Offset Current Comp.: ±10 µA, adjustable by control voltage (LEMO pin 4, 5. ±5 V is equivalent to ±100 µA offset current)
  • Offset Control Input Impedance: 25 ΚΩ
  • Input Current Range: ±200 μΑ
  • Input Offset Voltage: - 100 mV (±2%)
  • BIAS for MCT DC Input Impedance: 50 Ω (Virtual) || 5 pF
• Output
  • Output Voltage Range: ±10 V(@ >100 kΩ Load)
  • Output Impedance: 50 Ω (terminate with >100 kΩ for best performance)
  • Max. Output Current: ±20 mA (Linear Amplification)
• Power Supply
  • Supply Voltage: ±15 V
  • Supply Current: ±30 mA typ.
• Case
  • Weight: 210 g (0.5lb)
  • Material: AIMg4.5Mn, nickel-plated
• Temperature Range
  • Storage Temperature: -40 ~ +100C
  • Operating Temperature: 0~+60C
• Absolute Maximum Ratings
  • Input power: ±5 V
  • Power Supply Voltage: ±22 V
  • Offset Control Voltage: ±12 V
• Connectors
  • Input: BNC
  • Output: BNC
  • Bias Voltage Output: center pin of BNC input socket
  • Power Supply
    • Lemo series 1S. 5 pin fixed socket (see drawing)
    • Pin 1: +15V
    • Pin 2: GND
    • Pin 3: -15V
    • Pin 4: external offset control port, apply positive voltage
    • Pin 5: reference for Pin 4

Attention: When switching the amplifier on or off a voltage spike of up to ± 600 mV may appear at the amplifier input which could damage sensitive detectors connected to the input. It is recommended to disconnect any detector from the input before switching the amplifier on or off.