Just a small explanation of the name bucket brigade delay.
Imagine a line of 10 fire fighters. One side is fire and the other side is water. Buckets of water has to be moved from the water source by buckets to the other to kill the fire.
Since the fire fighters are in a line, when they receive a bucket of water, they can't deliver to the next person. Similarly when they deliver water to the next person, they can't receive water.
A BBD chip in similar, has tiny line of capacitors (say 511) inside representing the buckets. Electronic switches (say 512) are in between each capacitor and the switches represent the fire fighters.
The odd numbered switches and even numbered switches are turned On and OFF alternatively from the square wave signals.
When the odd numbered switches are turned on, they transfer the charge from the left side capacitors (input side) to the right side capacitor. When the even numbered switches are turned on, they transfer the charged capacitor value to the next and so on.
At the output, switches 511 and 512 outputs are connected together so there is a continuous signal flow. Now there is signal at the output but chopped at the same frequency as the square wave.
Since this chopped frequency is 30 Khz or more, a low pass filter of 20 Khz is inserted at the output to filter out all higher frequency above audible range. If the portion of signal is fed back to the input to create a flanging or echo, another low pass filter is required at the input before the BBD.
Since the stages work similar to the bucket brigade fire fighters, hence the name bucket brigade delay line.
To prevent loss of signal (leakage of capacitors) during modulating frequency transition, the driver chip is interlocked internally cmos or ttl gates so the rise and fall of the wave forms never cross each other.
Regards.
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