Patent GB-455497-A (GB)
Title: Improvements in and relating to generators of electrical oscillations
IPC: H03K4/18
Filed: 1935-03-21
Abstract: 455,497. Valve circuits for generating oscillations. WHITE, E. L. C., 32, The Rise, Hillingdon, Middlesex. March 21, 1935, No. 8898. [Class 40 (v)] In an oscillation generator of relaxation type comprising a valve having at least two grids in addition to the anode, that nearer to the cathode being maintained at a positive potential and the two grids being coupled together, e.g. by a condenser, the grid nearer the anode is connected to the cathode by a limiting device such as a diode valve to prevent its potential from substantially exceeding that of the cathode. The action of the oscillator is explained with reference to Figs. 1 and 2. The valve 1 is operated in a condition of anode current saturation so that if a negative impulse is applied to the grid 5, and the current to anode 4 thus falls, that to anode 3 increases. The voltage of 3 thus falls owing to the increased voltage drop in R1, and, owing to the coupling condenser C1, the negative potential on the grid is increased. This goes on until substantially the whole of the emission is reaching the anode 3 and accordingly there is now a period in which the current to 3 continues at its maximum and the voltage on 5 gradually falls to the point at which the anode 4 again takes current. The current to 3 is thus reduced and its voltage rises accelerating the discharge of C1 and giving it a charge in the opposite direction. This charge is dissipated by flow of grid current. The voltage on the grid thus follows the course shown in Fig. 2. In the arrangements described below the oscillation-producing grid nearer the cathode corresponds to the anode 3 and the other to the grid 5. In the heptode oscillator shown in Fig. 4, for generating a saw-tooth voltage by the periodical discharge of a condenser C3, G3, G4 are the grids concerned in the production of oscillations, G2 and G5 being connected to G3 without materially affecting the action. The diode D prevents G4 from assuming a voltage much in excess of that of the cathode. Frequency controlling impulses are given to G1 which however may be omitted if the control impulses are given to one of the other grids. An additional grid connected to the cathode may be provided between the anode and the other grids to enable the apparatus to function correctly even if the anode voltage swings lower than that of the grid G5. The condenser C3 and resistance R3 may be omitted, the currents generated being taken from the anode circuit. The frequency of oscillation is dependent on the values of condenser C1 and resistance R2. In a modification, Fig. 6 (not shown), the grid G4 is given a positive voltage from a potentiometer and the arrangement generates square topped pulses like a multi vibrator and can be used for frequency division. Fig. 8 shows a similar circuit in which the diode D uses the same cathode as the oscillator. Grids G4, G5 are connected as screen and suppressor grids respectively. The saw-tooth generator shown in Fig. 9 uses a triode-hexode, the triode grid taking the place of the diode anode in previously described arrangements and the periodical discharge of C3 taking place through the anode - cathode space of the triode. If the condenser B is omitted the arrangement can be used as a frequency divider. A triodehexode may be used also for generating squaretopped pulses. Frequency dividers of the above kind may be used in cascade.