DLPCA-200 Low Noise Current Preamplifier

The DLPCA-200 is an I/V conversion preamplifier developed and manufactured by the German brand FEMTO. It features an input noise as low as 4.3 fA/√Hz, a bandwidth of up to 500 kHz, and a variable gain range from 10³ to 10¹¹ V/A.

The DLPCA-200 variable gain transimpedance amplifier offers multiple functions and is specifically designed for various applications requiring the conversion of small currents into usable voltages. It is highly suitable for time-resolved current and charge measurements in the μs range, as well as serving as a preamplifier for photodiodes or lock-in systems.

The DLPCA-200 offers variable transimpedance gain from 10³ to 10¹¹ V/A, enabling sensitive measurements of currents ranging from sub-picoamperes to milliamperes. Its switchable AC/DC coupling, 10 Hz low-pass filter, and adjustable offset control allow the amplifier to adapt to different measurement tasks and signal conditions. It provides an adjustable bias voltage connected to the input socket's shield to optimize the speed and noise performance of external photodiodes connected to the amplifier input.

The FEMTO DLPCA-200 is highly stable due to FEMTO's integrated input protection circuitry. It protects against high-voltage transients of up to +/- 3 kV from a 200 pF power source (similar to what you would expect when a statically charged person touches the amplifier input). The electrostatic voltage protection ranges from -16 V to +12 V. You can simply plug and unplug cables as needed. FEMTO rarely experiences electrostatic damage to amplifier chips because of the integrated input protection. However, caution is advised when using high-voltage power supplies nearby, as depending on the power supply's capacitance, a significant charge could flow into the amplifier during an accidental short circuit in your setup, damaging the input stage. If using long cables (equivalent to high capacitance) that may be charged to voltages exceeding the above values, take precautions and properly discharge the cables before they damage the amplifier. When a 50-ohm terminator is connected to the input, overload activation occurs due to the nature of the transimpedance amplifier (TIA). Unlike voltage amplifiers, a TIA ideally expects a very high impedance source. If the source becomes low impedance, the TIA exhibits additional voltage gain, and any offset present at the amplifier input can drive the amplifier into saturation. This does not harm the TIA but triggers the overload indicator to signal that the amplifier is not operating correctly (due to the low source impedance). Simultaneously, you will measure a constant + or - 10 V at the output because the amplifier is saturated. After removing the 50-ohm terminator, the TIA will return to normal operation within a few milliseconds.