Design of bipolar imaging device (BASIS)

The design methodology of a bipolar imaging device, BASIS (base-stored image sensor), with a capacitor-loaded emitter-follower circuitry, is established by analyzing the basic operation of BASIS and the generation mechanism of fixed pattern noise where theoretical results coincide well with experimental results. From this methodology, a wide dynamic range of linearity is assured by optimizing the forward-bias voltage in readout operation, while high sensitivity is realized by making the base-to-collector junction capacitance C _bc as small as possible and by designing the emitter common current gain h_FE of a phototransistor in a pixel to be as high as possible. In order to reduce fixed pattern noise, nonuniformities of h_FE and C_bc should be made as small as possible by improving fabrication process technology, while the bootstrap factor k_f defined in this theory should be as small as possible