The H7680 series of gated photomultiplier tube (PMT) units from Hamamatsu Corp. have a spectral response from 300 to 650 nm with the wavelength of the maximum response at 420 nm. The units feature a repetition rate of 100 kHz, 107 minimum switching ratio, 20-ns rise/fall time of the gate and 25-mm-diameter photocathode effective area. Gate pulse width is 30 ns for the H7680-01 and 100 ns for the H7680, while gate noise at 50 (omega) is 60 mV p-p for both units. The built-in PMTs have 95-µA/lm luminous cathode sensitivity and 475-A/lm anode sensitivity. Other specifications include a 1.7-ns anode pulse rise time, 16-ns electron transit time and 500-ps transit time spread. The H7680 series is suitable for laser radar, factory automation systems and fluorescence lifetime measurements.