GB313448A - Electrical oscillation circuits - Google Patents

Abstract

313,448. Kolster - Brandes, Ltd., (Assignees of Crossley, A.). June 11, 1928, [Convention date]. Thermionic generators. - A piezoelectric oscillator employing a screened-grid valve or valves, produces oscillations inde - pendent of the frequencies fixed by the inherent capacity effects existing between the valve electrodes. The piezo-electrode crystal 1, Figs. 1, 2 is connected between the control grid 18 and the filament 17, of valve 5, grid bias being supplied from a source 3, through a radio - frequency choke 2. Coupling between grid and plate circuits is by means of variable condenser 12, and the screen-grid 16 is positively biassed from a tapping 15 on the anode supply 6 which may be in series, Fig. 1, or in parallel, Fig. 2, with an oscillatory circuit comprising inductance 7, variable capacity 8 and ammeter 9. In the latter case a radio-frequency choke 13 is connected between the anode 19 and the anode supply 6, the latter in each case being shunted by a condenser 10, while a condenser 11 shunts the screen-grid supply. An inductive coupling through coil 14, Fig. 3, may be provided which opposes and limits the capacitative coupling produced by the condenser 12. A push-pull arrangement, Fig. 4, may be used in which the crystal 1 is connected between the valve grids 18, 18<1> of the two valves 4, 4<1>, a common grid battery 3 biasses both grids through radio-frequency chokes 2, 2<1>, a common anode supply 6 feeds both anodes 19, 19<1> through a common oscillatory circuit 7, 8, and tappings 15, 15' on the anode supply 6, bias the two screen grids 16, 16'.