GB763850A - Improvements relating to electronic frequency selective circuit arrangements - Google Patents

Abstract

763,850. Discharge tube selective amplifying circuits. BRITISH THOMSONHOUSTON CO., Ltd. April 20, 1955 [April 7, 1954], No. 10239/54. Class 40(6) In an amplifier having a feed-back circuit including a pair of resistor-capacitor networks, the networks are tuned to the same frequency and arranged in cascade to give a band-pass or band-stop effect. A band-pass amplifier is obtained, Fig. 4, by employing two networks F1, F2 arranged in the feed-back loop round a discharge tube V1. Each network has an amplitude response and phase response as shown in Figs. 2 and 3. At frequencies near f the two circuits give a small positive output so that peaks occur at frequencies f1, f2, Fig. 5, while at frequencies further removed from f the feed-back is negative. In a practical embodiment, Fig. 7, the filter networks F1, F2 are isolated by cathode followers V2, V3 the networks being shunted by capacitor C7 and resistor R10 to flatten the response (Fig. 8, not shown). A band-stop effect may be obtained (Fig. 10, not shown) by employing a Wien bridge.