The bucket brigade device: An analog shift register
Nowadays, digitally delaying audio is easy, but historically we had to use devices like the TCA350, a fully analog delay line:
It works by charging a small capacitor to the input voltage, and then moving that charge through a chain of hundreds more before it exists the device:
The two clock signals consist of non-overlapping negative pulses, each making every other MOSFET momentarily conduct. Additionally, each pulse changes the voltage (but not charge) on every other capacitor, which helps pull charge from one stage to the next, preventing the samples from just smearing out.
The pads marked with yellow are connected to pins, which how the chip interacts with the outside world. The ground pin, on the lower left, is directly connected to the bulk silicon, ensuring that the body diodes of the transistors never conduct, because – in typical 1970s electronics fashion – the chip uses voltages below ground, not above it.
There is a single MOSFET transistor in the red box, with the gate coming in from the left, and the drain and source going off the chip. This is T187 on the schematic, and is responsible for amplifying the output right before it leaves the chip.
