Patent ID: 7902577

Claim:
An image sensor comprising: a photo diode (PD) configured to receive an image optical signal to generate a first optical current having a cathode connected to a power supply voltage terminal; a heterojunction bipolar transistor (HBT) having a floating SiGe base, a Si collector, and a Si emitter, the floating SiGe base connected to an anode of the PD, the Si collector connected to the cathode of the PD, and the Si emitter from which an amplified sensing signal is generated; a reset PMOS transistor for connecting the emitter of the HBT with a ground voltage terminal in response to a reset signal applied to a gate of the reset PMOS transistor; and a selection PMOS transistor for externally transmitting an emitter signal of the HBT in response to a selection signal applied to a gate of the selection PMOS transistor, wherein the image sensor is configured to function as a pixel formed by the HBT, the reset PMOS transistor, and the selection PMOS transistor, wherein HBT is configured to sense and amplify the first optical current while the image sensor performs as the pixel, and wherein the base of the HBT is configured to generate the first optical current when the image optical signal is incident to the PD, and wherein the base of the HBT is configured to amplify and generate a high current in a reverse bipolar operation from the image optical signal being incident to the PD.