VLQC is a quenching circuit designed in our laboratories to perfectly suit the constraints of an array, i.e. high compactness, cross-talk avoidance and low afterpulsing. In VLQC a single transistor performs the sensing, quenching and reset tasks drastically reducing the overall detector parasitic capacitance and thus system power consumption, pixel-to-pixel optical coupling and afterpulsing.

The main advantages of VLQC are:

• Reduced number of transistors
• Only two transistors directly connected to the SPAD anode
• Customizable holf-off time (from 40ns up to 2us)
• Detection of photons absorbed during the reset phase

The picture below shows a test integrated circuit comprising the VLQC. A part from the output buffer that is necessary to drive pads, VLQC area is comparable with a 20um SPAD area.

Publications

• S. Tisa, F. Guerrieri, and F. Zappa:
  "Variable-Load Quenching Circuit for single-photon avalanche diodes"
  4 February 2008 / Vol. 16, No. 3 / Optics Express 2232
  

Contacts

Franco Zappa - zappa@elet.polimi.it
Simone Tisa - tisa@elet.polimi.it