Digital Ultra Low Noise Boxcar Photodiode Integrator with USB


The IPD4B is a highly-integrated boxcar integrator to be attached directly to up to four photo diodes. After a trigger pulse, all four inputs are integrated simultaneously for an adjustable amount of time between 6 μs and 1 second (boxcar integrator). The measurement is digitized using integrated 20 bit analog-to-digital converters with ultra low noise and exceptional dynamic range. Integration results are transferred over the USB link to a computer (alternatively: 3.3 V UART, SPI, I2C).

In a triggered mode, the IPD4B can continuously acquire four signal measurements and transfer them over the USB link at a trigger rate of up to 1.1 kHz. This allows shot-to-shot measurements in systems with 1 kHz repetition rate. Internal triggering additionally allows gap-less boxcar integration mesurements with gate times 500 μs to 1 s e.g. for monitoring.

The USB interface registers itself as virtual serial port (VCP) for direct and easy integration into lab control software such as LabView. Communication uses a simple text-based protocol.


  • Simultaneous integration of up to four inputs at up to 1.15 kHz
  • Each measurement includes signal and background acquisition
  • Adjustable gate time 6μs to 1s with internal timer (*)
  • High accuracy, low drift
  • Tunable full scale range 12pC to 350pC
  • Easy-to-use USB interface
  • Very high resolution due to 20 bit ADC
  • Extremely low noise integrator:
    For 350pC full scale range <10ppm noise and <20ppm noise down to 50pC full-scale range (typ.)
    This corresponds to a dynamic range in excess of 1:105
    Shot noise limited for many applications
  • External trigger rising or falling edge (TTL or LVDS) (*)
  • Tunable trigger delay up to 1 second: (*)
    This eliminates the need for an external delay generator and can be used to achieve "negative" delays for repetetive triggering.
  • Internal trigger with adjustable rate up to 1 kHz (*)
  • Additionally allows continuous gap-free integration for gate times 500 μs to 1 s on all four channels simultaneously
  • Small form factor: 60 x 40 x 22 mm (*)
  • Comes with easy to use LabView drivers
  • (*) marks improvement over the IPD4A

Typical Applications

  • Laser pulse monitoring and signal
    measurement in 1 kHz systems
  • Shot-to-shot pulse noise measurements
  • Digital two or four segment photodiodes

Application Notes

Femtosecond fluorescence spectroscopy based on the optical Kerr effect
(applies predecessor IPD4A)
R. Mundt, G. Ryseck, P. Gilch, Femtosecond spectroscopy group, Chemistry, University of Düsseldorf, Germany (May 2014)

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