US2866093A - Mains/battery amplifying apparatus - Google Patents

Description

Dec. 23 19 58 H. T. J. WIEGERINCK 2,866,093

MAINS/BATTERY AMPLIFYING APPARATUS Filed July 19, 1954 Inventor yam/ms fc/ MfGE/W/VC'R Attorneys United States 6 Claims. 01. 250-47 The present invention relates to electronic apparatus which may be operated either from the supply mains or batteries, and of the kind (hereinafter referred to as the kind described) comprising a number of filamentary type electron tubes and an indirectly-heated cathode type output tube which is used in the circuit during operation from the supply mains, and has its heater supplied by the supply mains; and in which during operation from the supply mains, the filament current for the filamentary type electron tubes is derived from the high tension supply through the cathode type output tube. More particularly, the present invention relates to improvements in or modifications of the apparatus disclosed in my copending United States application No. 290,002 filed 26th May 1952, now Patent No. 2,712,066, issued June 28, 1955, which describes and claims an electronic apparatus of the kind described, in which a D. C. connection is provided between the grid of the cathode type output tube and a load connected in series with one of the filamentary type electron tubes (hereinafter called the stabiliser tube), when operating from the supply mains, whereby the voltage developed across said load may be applied to the cathode type output tube to control its conductance to compensate for fluctuations of the supply voltage and to stabilise the cathode voltage of said cathode type output tube, from which the filament current is supplied to the filamentary type electron tubes, at a substantially constant value.

According to the present invention, the stabiliser tube has a screen grid which, when the apparatus is operating on the supply mains, is fed both directly from the unstabilised high tension supply and also from the stabilised voltage at the cathode of the cathode type tube, said latter connection being made through a resistor.

Preferably, the feed from the unstabilised high tension supply is derived from a network of resistors connected across the high tension supply, the screen grid being connected to an intermediate point on the resistor network.

According to one form of the invention, one of the filamentary type electron tubes which is used for example, as an amplifier when operating from batteries, is employed when operating from supply mains, solely to perform the function of the stabiliser tube controlling the conductance of the cathode type output tube, the remaining filamentary type electron tubes providing the necessary amplification or other functions of the apparatus. Alternatively, the filamentary type electron tube employed as the stabiliser tube when operating from the supply mains may also serve as an amplifier stage or perform another function in the apparatus, for example, it may also function as an amplifier driving the cathode type output tube. When operating from batteries, this filamentary type electron tube can function simply as an amplifier stage.

2,866,093 Patented Dec. 23, 1958 stood, two embodiments thereof will now be described with reference to the accompanying drawings in which:

Fig. 1 is a circuit diagram of one embodiment of the invention, and

Fig. 2 is a circuit diagram of a modification.

Both Figure l and 2, show circuit diagrams of lowfrequency amplifier stages, which may comprise the output stages of a mains/battery radio receiver. Referring to Fig. 1, tube V1, which is a filamentary type electron tube, serves solely as a stabiliser tube controlling the conductance of tube V2 which is a cathode type output tube having the primary winding of a loudspeaker transformer T1 connected in its anode circuit. Tube V3 is also a filamentary type electron tube serving as a low-frequency amplifier stage driving tube V2. The output of tube V3 is fed to the control grid of tube-V2 through condenser C1, and the anode of the stabiliser tube V1 is D. C. connected to the control grid of tube V2 through resistor R6. The filaments f and f of tubes V1 and V3 are connected in series with the cathode of the cathode type output tube and are supplied from the current flowing through that tube from the high tension positive supply, together with the filaments f and f of other filamentary type electron tubes forming other stages of the apparatus. The cathode type tube V2 has its cathode heated by the heater h fed from the supply mains. The high tension supply for the drive-amplifier tube V3 is obtained from the stabilised voltage at the cathode of the cathode type output tube V2 through the resistor R1. The high tension supply for the cathode type output tube is obtained from the unstabilised positive high tension supply through the primary of the output transformer T1, and this supply also feeds the anode of the stabiliser tube V1 through resistor R2.

According to the invention, the screen grid of the stabiliser tube V1 is fed both from the unstabilised high tension supply by means of the resistor network R3, R4 connected across the high tension supply, the junction point of these two resistors being connected to the screen grid of tube V1, and also from the cathode of the cathode type ice ' output tube through the series resistor R5. Condenser In order that the invention may be more fully under- C2 is connected across the stabiliser tube V1 to prevent instability. The tube V1 may be the filamentary type output tube which is otherwise not used when working from the supply mains.

As will be explained later, the arrangement according to the invention provides improved regulationof the filament voltage which can thus be maintained more constant than the arrangement described in the aforesaid application No. 290,002, now Patent No. 2,712,066, issued June 28, 1955.

The arrangement shown in Fig. 2 is a modification of the circuit shown in Fig. 1, and like reference numerals have been used for like components. In this modified arrangement however, the stabiliser tube V1 also serves as the voltage amplifier driving the cathode type output tube V2 and hence amplifier tube V3 is omitted, and the anode of tube V1 is directly connected to the control grid of tube V2. This latter arrangement is less inherently stable than the circuit of Fig. 1 owing to the coupling between the power supply voltage and the screen grid of tube V1.

The stabilising action of both circuits is achieved by variations in the voltage across resistor R2, due to variations in the heater voltage oftube V2, controlling the conductance of tube V1, as in co-pending application No. 290,002 and the action producing the improved regulation of the heater voltage will now be explained. Suppose the high tension supply voltage increases; this will result in an increase of the screen voltage of tube V1 and as a result the anode current of this tube will increase also. As however tube V1 is a screen grid or pentode valve, the anode current increases approximately according to the square root of the cube of the driving voltage and hence the anode current of V1 will increase more than proportionately with the applied driving voltage. This voltage is determined by both the control grid and the screen grid voltages, but since the control grid voltage of tube V1 is substantially constant, the driving voltage is mainly determined by the screen grid voltage. It can be calculated that as a result of these characteristics, the filament voltage has a maximum for a particular high tension voltage, and experiments show that the variation of this high tension voltage results in only a very small change in the filament voltage. The more than linear increase in anode current with increase in screen voltage, and the connection provided between the screen grid and the unstabilised high tension supply serve to achieve the improved stabilisation of the cathode voltage of tube V2.

The addition of resistor R between the cathode of V2 and the screen grid of the tube V1 reduces the tendency to instability which may be caused by positive feed back between the anode of tube V2 and the screen grid of tube V1, and the cathode of tube V2 and the heater of tube V1. Resistor R5 also provides negative feedback between the cathode of tube V2 and the screen grid of tube V1.

It will be understood that only basic circuit arrangements according to the invention have been described and that various switches, for example, similar to those described in copending application No. 290,002 would be provided to switch the circuit connections when changing over from operation on batteries to operation from the supply mains and vice versa.

Whilst particular embodiments have been described, it

will be understood that various modifications may be made without departing from the scope of the invention.

I claim:

1. Electronic apparatus which may be operated from supply mains and batteries, comprising a plurality of filamentary type electron tubes, one of said filamentary type electron tubes serving as a stabiliser tube when operating on supply mains and having an anode, a control grid and a screen grid, and a cathode type electron tube having a heater, a cathode, and at least one grid electrode and having its heater supplied from the supply mains, mains connecting the filaments of at least some of said filamentary type electron tubes including said stabiliser tube in series with the cathode of said cathode type electron tube during operation from the supply mains, whereby the filaments of said filamentary type electron tubes are supplied from the current flowing through said cathode type electron tube, a high tension positive supply line, a resistive load connected in series between the anode of said stabiliser tube and the high tension positive supply line, a direct current connection between the anode of said stabiliser tube and a grid of said cathode type electron tube during operation from supply mains, a first direct current connection to the screen grid of said stabiliser tube from the cathode of said cathode type electron tube and a second and separate direct current connection to the screen grid of said stabiliser tube from the high tension positive supply line.

2. Electronic apparatus which may be operated from supply mains and batteries, comprising a plurality of filamentary type electron tubes, one of said filamentary type electron tubes serving as a stabiliser tube when operating on supply mains and having an anode, a control grid and a screen grid, and a cathode type electron tube having a heater, a cathode, and at least one grid electrode and having its heater supplied from the supply mains, means connecting the filaments of at least some of said filamentary type electron tubes including said stabiliser tube in series with the cathode of. said cathode type electron tube during operation from the supply mains, whereby the filaments of said filamentary type electron tubes are supplied from the current flowing through said cathode type electron tube, a high tension positive supply line, a high tension negative supply line, a resistive load connected in series between the anode of said stabiliser tube and the high tension positive supply line, a direct current connection between the anode of. said stabiliser tube and a grid of said cathode-type electron tube during operation from supply mains, a resistor connected between the cathode of said cathode type electron tube and the screen grid of said stabiliser tube, a separate direct current connection to the screen grid of said stabiliser tube comprising at least two series-connected resistors connected directly between the positive and negative high tension supply lines, and a connection between two of said resistors and the screen grid of said stabiliser tube.

3. Apparatus as claimed in claim 2, in which the direct current connection is provided between the anode of the stabiliser tube and the control grid of the cathode type electron tube.

4. Electronic apparatus which may be operated from supply mains and batteries, comprising a plurality of filamentary type electron tubes, one of said filamentary type electron tubes serving as a stabiliser tube when operating on supply mains and having an anode, a control grid and a screen grid, and a cathode type electron tube having a heater, a cathode, and at least one grid electrode and having its heater supplied from the supply mains, means connecting the filaments of at least some of said filamentary type electron tubes including said stabiliser tube in series with the cathode of said cathode type electron tube during operation from the supply mains, whereby the filaments of said filamentary type electron tubes are supplied from the current flowing through said cathode type electron tube, a high tension positive supply line, a resistive load connected in series between the anode of said stabiliser tribe and the high tension positive supply line, a direct current connection between the anode of said stabiliser tube and a grid of said cathode type electron tube during operation from supply mains, a connection between the cathode of said cathode type electron tube and the screen grid of said stabiliser tube, a connection between the high tension positive supply line and the screen grid of said stabiliser tube and a connection between the cathode of said cathode type electron tube and the control grid of said stabiliser tube.

5. Radio receiving apparatus which may be operated from supply mains and batteries, comprising a plurality of filamentary type electron tubes, one of said tubes serving as an output tube when operating on batteries and as a stabiliser tube when operating on supply mains and having an anode, a control grid and a screen grid, and a cathode type electron tube having a heater, a cathode, and at least one grid electrode and having its heater supplied from the supply mains, and used as an output tube during operation from the supply mains, means connecting the filaments of at least some of said filamentary type electron tubes including said stabiliser tube in series with the cathode of said cathode type electron tube during operation from the supply mains, whereby the filaments of said filamentary type electron tubes are supplied from the current flowing through said cathode type electron tube, a high tension positive su ply line, a high tension negative supply line, a resistive load connected in series between the anode of said stabiliser tube and the high tension positive supply line, 11 direct current connection between the anode of said sta biliser tube and a grid of said cathode type electron tube, a resistor connected between the cathode. of said cathode type electron tube and the scree grid of said stabiliser tube, a resistor network connected between the positive and negative high tension supply lines, a connection between an intermediate point on said resistor network and the screen grid of said stabiliser tube and a connection between the cathode of said cathode type electron tube and the control grid of said stabiliser tube.

6. Radio receiving apparatus which may be operated from supply mains and batteries, comprising a plurality of filamentary type electron tubes, one of said tubes serving simultaneously as an amplifier tube and as a stabiliser tube when operating on supply mains and having an anode, a control grid and a screen grid, and a cathode type electron tube having a heater, a cathode, and at least one grid electrode and having its heater supplied from the supply mains, and used as an output tube during operation from the supply mains, means connecting the filaments of at least some of said filamentary type electron tubes including said stabiliser tube in series with the cathode of said cathode type electron tube during operation from the supply mains, whereby the filaments of said filamentary type electron tubes are supplied from the current flowing through said cathode type electron tube, a high tension positive supply line, a high tension negative supply line, a resistive load connected in series between the anode of said stabillser tube and the high tension positive supply line, a direct current connection between the anode of said stabiliser tube and a grid of said cathodetype electron tube, a resistor connected between the cathode of said cathode type electron tube and the screen grid of the said stabiliser tube, a separate direct current connection to the screen grid of said stabiliser tube comprising at least two series-connected resistors connected directly between the positive and negative high tension supply lines and a connection between two of said resistors and the screen grid of said stabiliser tube and means for applying signals to the control grid of said stabiliser tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,220,051 Israel et al. Oct. 29, 1940 2,269,989 Root Jan. 13, 1942 2,712,066 Wiegerinck June 28, 1955

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