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  • Minimum Input Noise 270 fA/Hz
  • Bandwidth up to 400 MHz
  • Gain up to 106 V/A
  • Flat frequency response
  • Stabilized and Adjustable Bias Voltage Output for Biasing External Photodiodes
  • EMI Shielded Case

High Frequency Current Amplifiers – Only for Specialists?

Users of high frequency components are often confronted with problems including unwanted oscillation, poor ground shielding, nonlinearities, gain peaking and bandwidth reduction caused by poorly designed amplifiers. FEMTO High Frequency Amplifiers have been designed to eliminate such unwanted problems. Insensitive to signal source parameters and input wiring, FEMTO High Frequency Amplifiers perform meticulously within their specifications. No gain peaking, oscillation or significant bandwidth reduction will occur, even for source capacitances up to maximum 2 nF (for the HCA-1M-1M-C).

Bandwidth independent of Source Capacitance

Merely a few picofarads of source capacitance can drastically decrease the bandwidth of high frequency current amplifiers. However, FEMTO current amplifiers do not have this limitation and are not influenced by a wide range of source capacitance. No frequency compensation or special adaptation is needed and the bandwidth and gain are constant up to the maximum source capacitance specified for each model*.


Amplifier models shown with an additional “C” are optimized for handling very large source capacitances up to nanofarads. They are very useful for measuring fast signals down to nanoseconds with large area detectors. For detectors with even more than 2 nF capacitance we offer custom designed models. Please contact us for details.

Adjustable Offset and Bias Voltage

For a high degree of flexibility FEMTO`s HCA Current Amplifiers offer precise offset and bias control by two trimpots. The wide range of the adjustable input offset current compensation preserves full dynamics even for signals with large DC-components. The Voltage at the bias-output can be adjusted precisely from -12 to +12 Volts using the multi turn bias-trimpot.


Fast Detection with Large Area Photodiodes
Photodetection with PMTs and Photodiodes
Ionization Detectors
Pyro- and Piezoelectric Detectors

Variable Gain Current Amplifier Comparison

Current Amplifiers Selector

Model3-dB Bandwidth
(DC ...)
Noise Current
Transimpedance (Gain) [V/A]Rise/Fall TimeMax. Detector Capacitance
DHPCA-100Variable - see DHPCA-100 product page
HCA-1M-1M1 MHz270 fA1x106350 ns50 pF
HCA-1M-1M-C1 MHz3.5 pA1 x 106350 ns2 nF
HCA-2M-1M2 MHz340 fA1 x 106180 ns25 pF
HCA-2M-1M-C2 MHz3.5 pA1 x 106180 ns1 nF
HCA-4M-500K4 MHz490 fA5 x 10590 ns15 pF
HCA-4M-500K-C4 MHz3.5 pA5 x 10590 ns500 pF
HCA-10M-100K10 MHz1.1 pA1 x 10535 ns15 pF
HCA-10M-100K-C10 MHz3.5 pA1 x 10535 ns150 pF
HCA-20M-100K-C20 MHz3.5 pA1 x 10518 ns50 pF
HCA-40M-100K-C40 MHz3.7 pA1 x 10510 ns30 pF
HCA-100M-50K-C100 MHz3.8 pA5 x 1043.5 ns20 pF
HCA-200M-20K-C200 MHz4.9 pA2 x 1041.9 ns8 pF
HCA-400M-5K-C400 MHz21 pA5 x 1031.0 ns10 pF*
Low Noise Input/Output Cable available: CAB-LN1 Low Noise Cable
The maximum detector capacitance listed above means that up to this value the specified bandwidth (± 15 %) is guaranteed. Larger capacitances are also possible but will influence the bandwidth.
Output voltage  ±1.5 V @ 50 Ohm load. Offset adjustable by trimpot. Output short-circuit protected. Adjustable bias output (-12V...+12V) for biasing photodetectors. Power supply ±15V via 3-pin LEMO socket. A mating connector is provided with the device. Optional power supply PS-15 is available. For further information, please view datasheets.
* For the ultra fast models HCA-100M-50K-C, HCA-200M-50K-C and HCA-400M-5K-C a reduction in bandwidth up to 25% of the nominal values might occur if the source capacitance reaches the above noted maximum source capacitance values. Especially for these models short cables at the input and the use of low capacitance sources is of major importance.

Typical Performance Characteristics

FEMTO Product Catalog 

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