Patent ID: 9385158
Filing Date: 2016-07-05
CPC Classification: G06F,H01L

Claim Text:
1. A bipolar junction transistor (BJT) pixel circuit, comprising: a BJT transistor, a collector thereof coupled to a ground; a photodetector, having a first-end thereof coupled to a base of the BJT transistor, a second-end thereof coupled to the ground, the photodetector generating a first base current based on a light intensity of a light incident on the photodetector, wherein the light is illuminated from a light source; a feedback amplifier circuit, coupled to the base of the BJT transistor and an emitter of the BJT transistor, operative to increase an emitter voltage of the BJT transistor according to the light intensity; a shutter circuit, coupled to the feedback amplifier circuit, operative to control an exposure time of the photodetector according to a shutter signal; and a current generating unit, coupled to the base of the BJT transistor, generating a second pulsed base current to the base of the BJT transistor upon receiving a trigger signal; wherein the current generating unit generates the second pulsed base current responsive to the trigger signal causing a base voltage of the BJT transistor to drop while the feedback amplifier circuit operates to increase the emitter voltage of the BJT transistor so as to build up the base-emitter voltage to a predetermined voltage level when the light source turns on.