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Ultra-Fast Photoreceivers
Series HSA-X-S

  • Si and InGaAs Photodiodes
  • Wavelength Range from 320 to 1700 nm
  • Bandwidth from 10 kHz up to 2 GHz
  • Max. Conversion Gain 4.8 x 10V/W
  • Min. NEP approx. 14 pW/√Hz

Ultra fast photoreceivers with FEMTO’s GHz Technology

By combining state of the art photodiodes with the proven and outstanding FEMTO GHz amplifier technology we designed a new family of photoreceivers with a remarkable performance. The HSA-X-S offers an upper bandwidth limit of 2 GHz. Two models with either a fast Si or InGaAs photodiode cover a spectral range from 320 to 1000 nm and 850 to 1700 nm, respectively. Due to the sophisticated amplifier design the minimum NEP is just 14 pW/√Hz at a transimpedance of 5 x 103 V/A. This allows for the measurement of optical power levels in the ?W range with GHz speed. For the HSA-X-S-1G4-SI with silicon photodiode the effective active diameter is a remarkably large 0.8 mm due to the use of a ball lens in front of the detector chip.


  • Spectroscopy
  • Fast Pulse and Transient Measurements
  • Optical Triggering
  • Optical Front-End for Oscilloscopes and A/D Converters

Ultra-Fast Photoreceivers

Spectral Range320 ... 1000 nm900 ... 1700 nm
Bandwidth10 kHz ... 1.4 GHz10 kHz ... 2 GHz
Photodiode0.8 mm Øeff. Si PIN0.2 mm Ø InGaAs PIN
Rise/Fall Time (10% - 90%)250 ps180 ps
Transimpedance Gain5 x 103 V/A (inverting)5 x 103 V/A (inverting)
Max. Conversion Gain2.5 x 103 V/W (@ 760 nm)4.8 x 103 V/W (@ 1550 nm)
Min NEP26 pW/√Hz (@ 760 nm)14 pW/√Hz (@ 1550 nm)
Threaded M4 and 8-32 for mounting on standard posts. 25mm Ø flange compatible with microbench systems. Model with fiber optic input or DC monitor output optionally available. Output short-circuit protected. Power supply 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.
HSA-X Series Model Update

Characteristics of the New Models

  • inverting
  • better output matching coefficient S22
  • smaller 1/f noise → lower broadband noise at the output

Remark: Bandwidth is unchanged (limited by the photodiode)


Part Number Naming Convention:




1G4 or 2G

SI or IN




High Speed Photoreceiver. This acronym replaces “HSA-X-S” which did not yet refer to photoreceivers.

X differentiation to the HSA-Y series

I inverting (positive input voltage → negative output voltage)

1G4 or 2G Bandwidth 1, 4 GHz respectively min. 2 GHz

SI or IN Si respectively InGaAs photodiode

FC optical connector: Fiber Connector

FS optical connector: Free Space

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