Abstract: A high-frequency power oscillator includes a tetrode electron tube (5), a current source (3) and a voltage-limiting circuit (4). The current source (3) is connected to the screen grid of the tetrode (5). This limits the screen grid current when the voltage on the anode of the tetrode (5) is momentarily lower than the screen grid voltage. Between the screen grid and the cathode of the tetrode the voltage-limiting circuit (4) is inserted. This circuit starts to conduct above a predetermined threshold value. This forms a limit to the screen grid voltage so that is is possible to operate the tetrode (5) in a pulsating manner. The voltage-limiting circuit may comprise a triode (4) with a voltage source (2) providing a constant voltage between the grid and the cathode of the triode (4).
Abstract: Apparatus for zone refining rods of semiconductive material is disclosed including an RF induction work coil having a single turn lying in a plane generally transverse to the lengthwise axis of the rod and encircling the rod. The coil is part of an RF power oscillator circuit including a power amplifying device (e.g. a vacuum tube) having a control electrode and a power output electrode, the latter being connected through a voltage-blocking capacitance to an input node of an inductive-capacitive tank circuit. The tank circuit includes the work coil and a capacitance. One input side of the work coil is connected in a circuit to the input node capacitance being connected between the input node and the other input side of the work coil. A grounded center tap of the coil serves as a ground node of the tank circuit.The disclosure includes a circuit arrangement for supplying a signal of preselected magnitude to the control electrode for forcing the amplifying device toward desirable operating conditions.
April 13, 1978
Date of Patent:
September 2, 1980
Robert O. Gregory, Louis H. Fricke, Jr.