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High-Speed Current Amplifiers

HCA Series Current Amplifiers

  • 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

Click Part # to view pdf datasheet
Model -3 dB
(DC ...)
Noise Current
(Gain) [V/A]
Fall Time
Detector Capacitance
DHPCA - 100

Variable - see DHPCA-100 product page

HCA-1M-1M 1 MHz 270 fA 1 x 106 350 ns 50 pF
HCA-1M-1M-C 1 MHz 3.5 pA 1 x 106 350 ns 2 nF
HCA-2M-1M 2 MHz 340 fA 1 x 106 180 ns 25 pF
HCA-2M-1M-C 2 MHz 3.5 pA 1 x 106 180 ns 1 nF
HCA-4M-500K 4 MHz 490 fA 5 x 105 90 ns 15 pF
HCA-4M-500K-C 4 MHz 3.5 pA 5 x 105 90 ns 500 pF
HCA-10M-100K 10 MHz 1.1 pA 1 x 105 35 ns 15 pF
HCA-10M-100K-C 10 MHz 3.5 pA 1 x 105 35 ns 150 pF
HCA-20M-100K-C 20 MHz 3.5 pA 1 x 105 18 ns 50 pF
HCA-40M-100K-C 40 MHz 3.7 pA 1 x 105 10 ns 30 pF
HCA-100M-50K-C 100 MHz 3.8 pA 5 x 104 3.5 ns 20 pF
HCA-200M-20K-C 200 MHz 4.9 pA 2 x 104 1.9 ns 8 pF
HCA-400M-5K-C 400 MHz 21 pA 5 x 103 1.0 ns 10 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 O load. Offset adjustable by trimpot. Output short-circuit protected.
Adjustable bias output (- 12 V ... + 12 V) for biasing photodetectors. Power supply + 15 V 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 the datasheet.

* 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 (pdf)

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