| 摘要 |
The disclosure describes one unit cell of a PNPN photoswitch array for an image sensor, including a PNPN light-activated thyristor (LAT), in the form of a two-terminal device, and a load FET. The FET functions as a load and as an on-off switch in series. The output of is a voltage at a first n node that controls the FET switch that connect a voltage-ramp input line to a capacitor and a diode that are connected in parallel. The other side of the diode is the input source of the unit cell that feeds charge into a vertical CCD analog shift register. At the start of a cycle of operation, such as the beginning of a sweep of a radiation beam and prior to a pulse of a target reflection pulse, being directed onto the pnpn photoswitch, the voltage level at the first node is high. At the time when a pulse of radiation is directed onto the photoswitch the first node goes low turning the switching transistor off. The capacitor has a charge level at an analog value representative of the elapsed time between the beginning of the cycle, such as the beginning of a radiation beam sweep, an the occurrence of the pulse reflected from a target. At the end of a cycle the charge is transferred into a CCD readout register.
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