High Speed Position Sensing Detector with Signal Processing Circuit



  • 400 kHz Bandwidth
  • Analogue outputs of all sum and differential signals
  • Laser trimmed resistors
  • Inputs for external adjustment of offset voltages
  • Good thermal tracking
  • Small size


  • Analogue PSD front-end in displacement measuring systems for OEM as well as evaluation purposes.

The SiTek SPC PSD is a PSD with a 400kHz attached signal processing circuit. The PSD currents are output as bipolar voltages representing the position and intensity of the centroid of a light spot on the PSD. The intensity signal can be used for external normalisation of the position (difference) signal in regard to light intensity dependence.

Inputs are available for external adjustment of offset voltages.

In order to obtain maximum precision, high reliability and small size the SPC electronics are built using thick film technology and laser trimmed resistors on a 20,5 x 20,5 mm2 ceramic substrate. The SPC PSD is delivered with surface mount or DIL Leads.

SPC PSD Models

One Dimensional SPC PSD Series

Model No. Pkg. Type Active Area
1L2.5 SPC-PSD Surface Mount 2.5 x 0.6mm
1L5 SPC-PSD Surface Mount 5.0 x 1.0mm
1L10 SPC-PSD Surface Mount 10.0 x 2.0mm

Two Dimensional SPC PSD Series - Duolateral

Model No. Pkg. Type Active Area
2L2 SPC-PSD Surface Mount 2.0 x 2.0 mm
2L4 SPC-PSD Surface Mount 4.0 x 4.0 mm
2L10 SPC-PSD Surface Mount 10.0 x 10.0 mm

Test conditions: Room temperature 23 degrees celsius, Power supply voltage + 15 V, Light source wavelength 940 nm. Position non-linearity are valid within 80 % of the detector length.

Package: 16 pin ceramic substrate, 20,5 x 20,5 mm2, with protective window.

Block Shematics

Application Information

Inputs 2, 6, 7 and 14 are used for external offset compensating voltages. Such a voltage can, as shown in the figure, be derived from a voltage divider and connected to the SPC input through a suitable series resistor.