A wide-band feedforward amplifier

The design of a wide-band feedforward amplifier in the frequency range 30-300 MHz is described. Expressions are derived for feedforward amplifier sensitivity, and the effect of imperfect loop cancellation is described. The effect of circuit imbalance on gain and terminal impedances is investigated. The circuit is realized in thin-film hybrid form, and measurements show 20 dB of distortion improvement at 300 MHz. Practical aspects of circuit adjustment and operation are considered.