| 摘要 |
<p>A photo-detector comprising an array of SPAD (Single Photon Avalanche Diode) cells (50, 50'), wherein each SPAD cell includes a SPAD circuit (2, figure 1) and a readout circuit (4, figure 1) that has an output node (26, figure 1) and is configured to deliver an electrical current to the output node when the SPAD circuit is activated by a photon. The output nodes 26,26' of a plurality of the SPAD cells 50, 50' are connected to at least one common output line 56 whereby the currents delivered to the output nodes of the activated SPAD cells are added together (aggregated) to provide an output current Iout. The magnitude of the output current represents the activation rate of the SPAD cells. The SPAD circuit may be connected to the readout circuit through a buffer device (16 figure 1). The readout circuit may include a constant current device (20 figure 1) and a switch such as a MOS transistor (Ms figure 1) configured to control delivery of constant current to the output node 26. The switch may also be configured as a differential switch comprising for example source coupled MOS transistors (18, 18 figure 3) and a constant current source (20 figure 3). The photo detector may include a quench circuit (8 figure 1) to reset the SPAD or APD (avalanche photo diode) (6 figure 1). The readout circuit may also include sample and hold circuitry and a timing device (figure 9).</p> |
