Bucket chain storage
A BBD ( English bucket brigade memory , BBM, or bucket brigade device , BBD) is a design of a delay line for analogue circuit for charge transport by the bucket brigade principle. Like a chain of buckets , the charges of the individual components are passed on from one to the other. The transport is synchronized by a clock generator. This makes the bucket chain memory the analog counterpart to a shift register .
application
Bucket chain memories are available with different numbers of memory levels and taps as an integrated circuit (IC), which are used, for example, for electronically generated reverb and echo effects. However, applications in audio technology are now less common, as the series connection of several analog stages has an unfavorable effect on the noise behavior.
The bucket chain principle is mainly used today in CCD cameras. The charges collected by the one- or two-dimensionally arranged semiconductor components are processed and transported sequentially.
functionality
A weakly p- doped silicon single crystal is oxidized on the surface to isolate the electrodes ( SiO₂ ). The metallic electrodes are flat and almost touch each other. If an electrode ( + V ) is activated positively in relation to the substrate, a flat area (yellow) is created below it, in which the edge of the conduction band is shifted below the Fermi level , so that the conduction band can absorb electrons (blue spheres) there ( potential well ) . Before the clock pulse ends at one electrode, the clock pulse of the adjacent electrode in the transport direction begins. In this overlapping phase, the electrons are distributed in the double-wide potential well. Of every three adjacent electrodes, at least one is always activated and at least one is not activated, so that the charge packets are transported separately from one another.
Components
Common bucket chain ICs are e.g. B .:
literature
- Siegfried Wirsum: NF tricks for the audio freak . 1st edition, Franzis, Munich 1990, ISBN 3-7723-3321-4