We developed a pulse generator that uses high‐voltage step recovery diodes to produce 400‐ to 500‐V pulses with rise and fall times of 0.8 ns. The output pulse width is continuously adjustable. For a pulse width of 0.8‐ns FWHM, the amplitude into 50 &OHgr; is 400 V. With the pulse‐width control set at maximum, the output pulse amplitude is about 500 V and the width is 3.5‐ns FWHM. The delay of the output pulse with respect to the input trigger is 38 ns with a jitter of about ±30 ps. An unusual feature of the pulse generator is that the 38‐ns delay time to the centroid of the output pulse is approximately constant and independent of the pulse width.