US2259471A

US2259471A - Thermionic circuits and method

Info

Publication number: US2259471A
Application number: US262123A
Authority: US
Inventors: Edward R Jahns
Original assignee: Tung Sol Lamp Works Inc
Current assignee: Tung Sol Lamp Works Inc
Priority date: 1939-03-16
Filing date: 1939-03-16
Publication date: 1941-10-21
Anticipated expiration: 1958-10-21

Description

Oct. 21, 1941. E. R. JAHNS THERMIONIC CIRCUITS AND METHOD Filed March 16, 1939 2 Sheets-Sheet 1 INPUT INVENTOR Edward RJa/ms )2 M 677A," ATTSRNEYS Oct. 21, 1941. JAHNS 2,259,471

THERMIONIC CIRCUITS AND METHOD Filed March 16, 1959 2 Sheets-Sheet 2 5WITCH INPUT INVENTOR Egz uard RJa/"ms 3%] f M ATTORNEYS Patented Oct. 21, 1941 I U 1 TED TAT-Es Pierm so FFI CE 7 V TI' IERMIGNIG AND METIIOD v corporation of Delaware Application Marchlfi, 1939, Serial N0. 262,123 Claims. (01. 25027) The present invention relates to circuits of the type usedin radio receivers, amplifiers or the like and comprises a new method of providing heater power for indirectly heated cathode tubes which improves the operation of the tubes and which utilizes one element-to perform: the functions which heretofore required the provision of two or more separate elements. The invention includes also new circuit arrangements suitable for carrying out the new method.

object of the invention is to provide a method of and means for suppressing the hum in tubes employingother than pure D. as a source of power for indirectly heated cathodes.

A'further object of the invention is to improve the operation or radio receiver's, amplifiers or the like employing alternating current or any source of supply other than pure direct current.

These and other objects o'f the invention will become apparent as the description proceeds.

For an understanding of the invention reference may be had to the accompanying drawings, of which:

Fig. 1 is a diagram illustrating generally the principle of the invention;

Fig. 2 is a circuit diagram illustrating one embodiment of the invention as applied to a simple A. C. operated amplifier; and

Figs. 3 and 4 are circuit diagrams illustrating modified forms of the invention as applied to radio receiving circuits.

The general theory of the invention may be readily understood by reference to Fig. 1 in which four tubes, I, 2, 3 and 4, having cathodes 6 and heater elements I, 8, 9 and III are diagrammatically illustrated. The particular number of tubes is of course immaterial. The circuit may include a greater or less number of tubes. Tubes I, 2, 3 and 4 may be any four tubes of an A. C. operated radio set or amplifier connected in any order.

In accordance with the invention, the A. C. "hum of tubes I and 4 is eliminated. by passing cathode current from one or more tubes of the circuit through heaters I and I0. Heaters 8 and 9 of tubes 2 and 3 operate as usual on A. C. voltage. The cathode current or currents passing through heaters I and III give a bias voltage to the tube or tubes supplying the current and consequently two bias resistors can be eliminated from the circuit.

Specific circuits embodying the invention will now be described.

In Fig. 2 is shown a simple A. C. amplifier cirl2whichis grounded at one end and connected at its other end to the cathode I3 of the power output tube I4 to serve as a bias resistor for that tube. The heater I5 for the cathode I 3 of the output tube is supplied-asusual from the A. C. source through the transformer I I).

Theyrest'of the circuit-being of conventional type needs no particular description. I The rectifier I! for supplyingthe plate voltage to tubes I I and I4 may be of the type known as #80, tube I I may be of the type known in the trade as GK? and the power output tube I4 may be of the type known as 6V6. A bleeder resistor I8 connected between the cathode I3 and positive voltage connection I9 may be employed if desired but it is not essential.

In Fig. 3 a conventional rad-i0 receiving circuit havingan amplifier 20, detector 2 I, power output cuit in which the amplifier tube II has a heater 55 tube 22 and rectifier 23 is shown. The heater 24 for the -cathode 25 of detector 2| operates as the bias resistor for the grid 26 of the power output tube 22." For this purpose the heater24has one end grounded and its other end connected to the negative voltage connection 21.

Another specific embodiment of the invention is shown in Fig. 4 wherein is illustrated a conventional type radio amplifier having the

audiofrequency amplifiers

28 and 29, push pull power output tubes 30 and 3|, and rectifier 32. The heater 33 for the cathode 34 of amplifier 28 together with the heater 35 for the cathode 36 are so connected as to serve as the bias resistors for the grids of

tubes

29, 30 and 3I and to receive current from the direct current portion of the circuit. For this purpose one end of heater 33 is grounded, as is cathode 36 and

cathodes

31 and 38 of output tubes 30 and 3|; the other end of heater 33 being connected through resistances 39 and 40 with the control grid 4| of amplifier 29 and through heater 35 with the low voltage line 42 of the rectifier 32.

From the above description of specific embodiments of the invention, it will be apparent that hum is eliminated in one or more tubes of a circuit by supplying the cathode heaters of such tube or tubes with current from the direct current portion of the circuit and that separate bias resistors for other tubes ofthe circuit are thus eliminated. In practice it has been found that the use of cathode current as heater power is moreefiective in suppressing hum than is the use of so-called direct current from a commercial power source unless such current is not pulsating and is strictly constant. Furthermore, the employment of a cathode heater in the norto stabilize the cathode currents by virtue of thecathode current, grid bias characteristics of the biased tube.

As the usual cathode current of a tube is ordinarily somewhat less than that supplied to cathode heaters by the separate source of voltage customarily used, the tube in which the heater is supplied with current from the direct current portion of the circuit should preferably be redesigned to allow for the lower cathode wattage as will be well understood by those skilled in the art. i

The following is claimed: v

1. In an alternating current operated circuit including a plurality of thermionic tubes, a cathode heater for one of said tubes and circuit connections for supplying said heater with the anode-cathode current of another of saidtubes whereby said heater is heated by unidirectional 7 current and said connections being such'as to enable said heater to serve as a bias resistor for said last-mentioned tube.

2. In an amplifier circuit or the like operating by alternating current and including at least one amplifier tube and an output tube, the combination comprising a cathode heater element for the amplifier tube,'a cathode and a grid for theoutput'tube and electrical connections between said amplifier heater and said output tube to cause thecurrent through the cathode'of said output tube to pass through said heater and the resulting voltage drop across said heater to operate as a bias voltage for the grid of said output tube.

3. In a radio receiving set operating by alternating current and having a detector, a power output tube and a rectifier having high and low voltage conections leading therefrom, the combination comprising a cathode heater for the detector and a cathode and grid for the output tube, one end of said heater being grounded and the other end of said heater being connected to the low voltage connection of said rectifier and to the grid of said output tube whereby said heater is supplied with unidirectional anode-cathode current from said tube and operates as a bias resistor for the gridthereof.

7 4. In an amplifier circuit operating by rectified alternating current and having at least one amplifier tube and an output tube, the combination comprising a cathode heater for the amplifier and a cathode and a grid for the output tube, said heater having one end grounded and having itsother end connected to said cathode of the output tube and said grid being connected to ground, whereby said heater serves as a bias resistor for said output tube.

5; In an amplifying circuit or the like operating by alternating current and having two amplifier tubes, two output tubes connected in pushpull relation and a rectifier having high and low voltage connections leading herefrom, the combination comprising a cathode heater for each amplifier tube, one end of one heater being grounded and one end of the other heater being connected to said low voltage connection of said rectifier and the other ends of said heaters being connected together to a point in the grid circuit of one of said amplifiers whereby said heaters are supplied with unidirectional current from said output tubes and operate as bias resistances for the output tubes and for said last mentioned am-, plifier.

EDWARD R. JAI-INS.