The bipolar transistor bucket-brigade shift register

An analysis of the bipolar transistor bucket-brigade shift-register operation is presented for comparison to other charge-transfer shift-register schemes. It is shown that incomplete charge transfer, the most important performance limiting effect for the charge-coupled device and the IGFET bucket brigade, is very small under most practical operating conditions for the bipolar transistor bucket brigade. In addition to charge loss due to finite transistor current gain h/SUB fe/ the next most important performance limitation comes from collector-emitter capacitance. It is shown that this collector-emitter capacitance leads to reduced analog time delay on transfer through the register and to signal attenuation effects similar to those resulting from incomplete charge transfer. Using the results of the analysis, experimental data reported by Sangster are discussed and a comparison of the advantages and disadvantages of the bipolar bucket-brigade register with the MOS charge-transfer registers is made.