Design of bipolar imaging devices (BASIS): analysis of random noise

A design methodology for a bipolar imaging device, the base-stored image sensor (BASIS), has been established by theoretical analysis and experimental verification for random noise. The random noise in BASIS is dominated by the shot noise in readout and transient reset operation. The theoretical analysis has been carried out by introducing the probability density functions for these operations. The readout noise depends on the base-to-collector junction capacitance C_bc , the emitter common current gain h_FE, the storage capacitor C_T, and the emitter voltage V _E. The reset noise has been confirmed to be given by thermal noise. The theoretical results coincide well with the experimental results obtained by TEG devices. An expression for the S/N ratio has been derived theoretically. It is found that h_FE should be made as large as possible and ( C_bc+C_be) as small as possible to improve the S/N ratio for random noise, where C _be is the base-to-emitter junction capacitance