Patent GB-620042-A (GB)
Title: Improvements in or relating to electrical amplifiers
IPC: G01C19/38
Filed: 1946-04-16
Abstract: 620,042. Thermionic valve amplifiers. SPERRY GYROSCOPE CO., Inc. April 16, 1946, No. 11713. Convention date, April 16, 1945. [Class 40 (vi)] [Also in Group XXXVIII] A thermionic valve amplifier has a differentiating network and an integrating network in the negative feed-back path, so that output contains terms proportional to the input, the time integral of the input and a time derivative of the input. A follow-up system, Fig. 1, for maintaining the phantom ring 4 of a gyro compass in alignment with the vertical ring 2, comprises an E-type pick-off 5, whose alternating output depends in magnitude and phase on the magnitude and sense of the relative displacement of the phantom and vertical rings. This output is applied via the two secondary windings of a transformer 13 to the grids of each section of two double triodes 17, 18. The alternating anode supply to the valves 17, 18, preferably from the same source 23 as the exciting current for the pick-off 5, is arranged so that, for an input in phase with the anode supply, the sections of valve 17 conduct on alternate half-cycles, producing an alternating output between points A, B. For an input in phase opposition to the supply, the sections of valve 18 conduct on alternate half-cycles, producing an alternating output between points A, B in phase opposition to that produced by valve 17. The sections of each valve 17, 18 have a common negative feed-back circuit comprising an integrating network composed of resistances 27, 28 respectively, shunted by a common condenser 30, and a differentiating network comprising resistances 32, 33 and a common condenser 34. This feed-back causes the gain of the amplifier to decrease to a minimum and then increase as the frequency is increased. The ends of resistances 27, 28 are joined by a balancing potentiometer 29 with an earthed wiper. Each condenser 30, 34 may be replaced by two condensers, one for each valve 17, 18. The alternating output appearing between A and B, containing terms proportional to the time integral and a time derivative of the input, as well as a term proportional to the input, is fed to power amplifier 39, 40. The amplified output is fed to one field winding of a two-phase motor 45, whose other field winding is preferably fed from the same source 23 as the anode supply to valves 17, 18. Motor 45 drives the phantom ring 4 through gearing 48, 50 to follow the vertical ring of the gyro-compass. In a modification, Fig. 3 (not shown), the outputs of valves 17, 18 are applied to the primary windings of a coupling transformer, the alternating anode supply being connected to the mid-taps of the primary windings. In another embodiment, Fig. 4 (not shown), a direct current output is obtained, the anodes of both sections of each double triode being connected to opposite ends of the secondaries of the anode supply transformer. The amplifier may be used as a demodulator, by arranging for the feed-back to be substantial at the modulation frequencies, to give an output dependent on the modulation and its time derivative and time integral. Specification 604,914 is referred to.