A drip manifold having drip nozzles configured to form controlled droplets is provided for use in wafer cleaning systems. A voltage depending on a voltage of an intermediate node between the second and fourth transistors is outputted as an output signal. The structure holds the seat in a stable state when the seatback is used as a table. The second channel can be configured to process the first term and the second term of the input vector using the first coefficient and the second coefficient of the filter.