An 80-Megabit 15-Watt Transistor Pulse Amplifier

High-power broadband amplifiers operating into impedances of less than 50 ohms have not been previously available. With the advent of optical modulators a need has arisen for such amplifiers. In particular an optical modulator 1 designed for experiments on optical communication systems requires a one-ampere peak signal to produce a one-radian phase shift. This modulator consists of a one meter long strip line partially loaded with a K D P (potassium dihydrogen phosphate) dielectric. The line impedance is 15 ohms. A P C M system was proposed requiring an 80-mc pulse rate and 10 to 12 nanosecond (ns) raised cosine pulses. The use of raised cosine pulses was dictated by the low-level vacuum tube pulse generator in the P C M system. A suitable driver for this optical modulator must deliver a one-ampere peak pulse into the 15-ohm line over a band extending from near dc to at least 100 mc. The discussion of the amplifier t h a t realizes these requirements is divided into several parts. Section II is a general description of the completed amplifier, including the configuration used and the results obtained. Section I I I gives the performance that was obtained, including photographs of the response to both square wave pulses and raised cosine pulses at rates up to 80 mc. The design considerations are taken up in detail in Section IV, and the mechanical construction is described in Section V. A discussion of the results is contained in Section VI. 1977