GB534531A - Improvements in high frequency amplifiers utilising electron discharge devices - Google Patents

Abstract

534,531. Valve amplifying circuits. BRITISH THOMSON-HOUSTON CO., Ltd. Aug. 4, 1939, No. 22648. Convention date, Aug. 5, 1938. [Class 40 (v)] Feedback, for neutralizing the effect of the grid-anode interelectrode capacity C2 is obtained by injecting the radio frequency potential appearing across an impedance 29 in the cathode lead into the tuned input circuit 18, 20. It is demonstrated in the Specification that the tuned output circuit 21, 26 together with stray capacity C4 constitutes with the impedance 29 a voltage divider, of such a nature that the voltage across 29. is out of phase with that between anode and cathode, and hence negative feed back can be obtained. In a modification, Fig. 2 (not shown), the impedance 29 is an inductance and the leads from the lower ends of the tuned circuit 18, 20 are interchanged. The impedance 29 may be constituted as a series tuned circuit so as to compensate for variation in amplification with frequency occuring in a tunable amplifier. The Specification as open to inspection under Sect. 91 of the Act discloses that positive feed back can be obtained if the leads are interchanged without changing the nature of the impedance 29 or vice versa. This subject-matter does not appear in the Specification as accepted.