Bucket Brigade Device

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A Bucket Brigade is an analogue delay line, developed in 1969 by F. Sangster and K. Teer of the Philips Research Labs. It consists of a series of capacitances C₀ to C_n. The stored analogue signal is moved along the line of capacitors one step at each clock pulse. In general, bucket brigades have been replaced by devices which use Digital Signal Processing. However, many swear that digital devices do not provide the same warmth and tone that bucket brigades do, and they still see use in specialty applications, such as guitar effects.

The name derives from a line of people passing buckets of water along the line.

A well-known integrated circuit device around 1980, the RETICON SAD-1024 implemented two 512 stage analog delay lines in a 16-pin DIP. It allowed clock frequencies ranging from 1.5khz to more than 1.5MHZ. The SAD-512 was a single delay line version. The TDA1022 similarly offered a 512 stage delay line but with a clock rate range of 5-500khz.

Despite being analog in their representation of individual signal voltage samples, these devices are discrete in the time domain and thus are limited by the Nyquist-Shannon sampling theorem; both the input and output signals are generally low-pass filtered. The input must be low-pass filtered to avoid aliasing effects, while the output is low-pass filtered for reconstruction. (A low-pass is used as an approximation to the Whittaker–Shannon interpolation formula.)

The concept of the Bucket Brigade Device lead to the Charge-Coupled Device (CCD) developed by Bell Labs.