| 摘要 |
684,805. Valve amplifying circuits; radio transmitting apparatus. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Aug. 17, 1951 [Dec. 21, 1950], No. 31174/50. Classes 40 (v) and 40 (vi). A push-pull multigrid valve amplifier is neutralized by means of cross-connected condensers 23, 24, each of which connects the screen grid of one valve to the control grid of the other. To prevent induced voltages due to the anode-anode voltage swing, the screen grids are connected to one another through a condenser 22 which may alternatively be of the centretapped type with the mid-point earthed. Very high order instability is prevented by means of series grid resistances 25, 27 which are shunted for normal working frequencies by inductances 26, 28, respectively. Each of the neutralizing condensers may comprise a flat or semi-cylindrical plate supported on the screen-grid pin of the corresponding valve holder, the co-operating electrodes comprising similar plates carried on a common insulating rod. In the case of semi-cylindrical plates, the rod is arranged to rotate and carries slip-rings, the cross-connections being clamped between insulating blocks and making connection to the corresponding slip-rings by means of brushes. |
