Niederfrequenzverstaerker mit einer Endstufe hohen Wirkungsgrades

摘要

869,577. Valve amplifier circuits. TESLA, NARODNI PODNIK. May 27, 1958 [May 25, 1957], No. 16854/58. Class 40(6). The invention relates to low frequency amplifiers of the type in which the input signal is in the form of width modulated pulses applied to a valve to render it fully conducting or non-conducting, the valve being connected to an inductive load and to any energy recovery diode so as to produce in an output circuit a mean current representing the modulation of the input wave. In the Figure the modulated input pulses are applied to the grid of a valve 1 which is connected to the HT supply through a pulse repetition frequency choke 41 and a low frequency choke 71. There is also provided a diode 2 which is connected through a further pulse frequency choke 4 to the load 8 and to a low frequency choke 7 connected to earth, the anodes of the valves being connected together through a capacitor 3 having a low impedance at the pulse frequency. A capacitor 5 having a larger value than capacitor 3 is connected between the outer ends of the chokes 4, 41, while a pulse frequency filter capacitor 6 connects the right-hand end of pulse choke 41 to earth. Fig. 2 shows the grid input voltage U g1 under various modulation conditions, the corresponding anode voltages U a1 of valve 1 and the anode currents I a1 , I a2 of valves 1 and 2. It will be seen that the mean anode current for unity mark space ratio of the input signal is nearly zero but varies from this value in accordance with the modulation. Chokes 7 and 71 may be two windings of a transformer in which case capacitor 5 may be replaced by a capacitor between the right-hand side of pulse choke 4 and earth.