US1957752A - Method and apparatus for amplifying frequency currents - Google Patents

Description

y 1934- J. M. AVERY 1,957,752 Y mam'on AND APPARATUS FORIAMPLIFYING FREQUENCY cunnsuws Filed Aug. -11, 1925 l l-r l l' lmm INVENTOR. Jo/v/v flI/EFK 1 ATTORNEY Patented May 8, 1934.

OFFICE METHQD AND APPARATUS FOR AMPIJFY- ZING FREQUENCY CURRENTS John M. Avery, Flushing, N. FL, assignor, by mesne assignments, to Radio Corporation of America, a corporation of Delaware Application August in, 1925, Serial No. c9522 it claims. (oi. ire-r11) This invention relates to the amplification of pulsating currents, particularly currents of low or audio frequencies such as are employed for example in telegraph and telephone systems.

in the amplification of alternating or pulsating currents, particularly at thelower frequencies, difficulty has been experienced in amplifying these currents without modification of their character. This dificulty has been particularly pronounced, for example, in the amplification of to certain inherent characteristics of such devices, and heretofore no satisfactory way of overcoming these difficulties has been devised.

An object of the invention is to provide an improved method and apparatus for amplifying pulsating currents, particularly by iron core transformers, with which amplification of the currents of all frequencies may be obtained without distortion or other undesired variations therein; and with which variations may be made in the char acter and range of the amplification.

A further object is to provide an improved ap-' aratus for amplifying pulsating currents which will accomplish each and all of the objects above set forth, and which will be relatively simple, easily manipulated, and inexpensive.

Various other objects and advantages will be apparent from the following description of one embodiment of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

in the accompanying drawing, 1 have illustrated a circuit arrangement embodying the invention and employing three cascade coupled vacuum tube relays.

In the accompanying drawing, the diagram represents the detector and amplifying circuits of a well known type of radio telephone and telegraph receiving set. In such a set the detector tube 1 is coupled by an iron core transformer 2- to an audio frequency amplifying vacuum tube 3 in the usual manner, and the tube 3 is in turn coupled by an iron core transformer 4 to a second audio frequency amplifying tube 5 in the usual manner. The filament electrodes 6 of the tubes are supplied with current by circuit wires 7 connected 'to a suitable source of energy A in the usual manner. High frequency currents, either directly from an antenna crcuit or from a radio frequency amplifying system, are impressed upon the input circuit 8 of the detector tube 1 in the usual manner.

The plate circuits of .the various tubes are supplied with current or potential from a suitable source, such as a battery B. For example wires 9, 10 and 11 connect the battery or other source of B potential with the primary windings of the transformers 2 and 4 and with the output circuit respectively. The primary windings of the transformers, and the other side of the output circult of the last tube, are connected by wires. 12, 13 and 14 with the platesv of their respective tubes, as usual in cascade couplings. The circuits just described may be the usual circuits employed for the cascade coupling of the tubes utilizing iron core transformers between successive tubes.

A variable resistance 15 is connected at one endby a wire 16 to the plate of the'detector tube 1, and at its other end by a wire 1'7 to one side of a suitable condenser 18, the other side of r the latter being connected by a wire 19 to the grid electrode of the next successive vacuum tube 3. The condenser and variable resistance 15 are thus connected in series with one another and in shunt across the iron core transformer 2. A similar coupling correspondingly indicated but with the exponent a added to the reference characters is provided between the audio frequency'amplifyingtubes 3 and 5 and across the transformer Preferably, although not essentially, the variable resistances 15 and 15a are connected for simultaneous operation by a single control, although such connection may be such as to permit of the independent adjustment of such resistances relatively to one another.

Without the by-pass circuits across the transformers 2 and 4, the system illustrated would amplify audio frequency currents of certain frequencies or of certain frequency bands with great efficiency should the condition exist that the impressed frequencies were ldentical with those for which the transformer-was most efficient, but for other frequencies outside these values a. lesser, distorted, and objectionable amplification would be given. By shunting, however, a portion of the audio frequency currents directly between the successivelycoupled' tubes and across the transformers'connecting them, those currents which are not efiiciently amplified by the transformers will be transferred between the tubes with some amplification and without amplification or distortion caused by the transformers.

1 sets, it has been found that tone values produced from this audio frequency amplifying system,

are dependent upon the values of the resistors 15 and 15a and the condensers 18 and 18a, and that the tones may be varied at will by variations of these elements in order that they might more readily by-pass currents of varying frequencies and frequency bands.

Inasmuch as one usually desires" to properly amplify given frequencies of currents, it is of advantage to couple the variable elements of the by-passcircuits for simultaneous operation by a single control as indicated on the drawing, but obviously they could be separately manipulated and adjusted, if desired. The coupling between the variable parts of the variable elements of the by-pass circuits permits of relative adjustment of the different variable elements in order that for any indication of the common operating membenthe efiect will be uniform in all by-pass circuits. By varying the adjustable elements of the by-pass circuits, separately or together, the character of the amplification may be varied and in radio telephone systems, the tone values amplified may be varied. B

The variable resistance 15 and condenser 1'7 constitute a variable impedance unit, and while other variable impedance units may be employed, I have found that this particular unit is very satisfactory. The variation of the impedance is easily and satisfactorily obtained by variation of the resistance, but obviously the condenser may also or instead be varied in order to vary the impedance.

- the primary and secondary windings of each transformer for variably shunting a portion of the audio currents around the coupling between successive relays whereby'said shunted currents are transferred without distortion.

2. An audio frequency amplifier comprising a plurality of thermionic relays, means including iron core transformers for coupling said relays successively, a by-pass circuit connected directly between the "anode and control electrode of successive relays and around the primary and secondary windings of each transformer for variably shunting a portion of the audio currents around the coupling between successive relays 3. An audio frequency amplifier comprising a plurality of vacuum tube relays, an iron core transformer coupling said relays to permit of the transfer and amplification of the audio currents between the same, and a by-pass circuit between the plate of one relay and the grid of the next successive relay, including therein a condenser and resistance, for shunting a portion of said current directly between said relays without distortion of the shunted current.

4. A frequency current amplifier comprising a plurality of vacuum tube relays, an iron core transformer coupling said relays to permit of the transfer and amplification of the currents between the same, and a by-pass circuit between the plate of one relay and the grid of the next successive relay, including therein a condenser and a variable resistance connected in series with one another and in said circuit, for shunting a portion of said current directly between said relays without distortion of the shunted current.

5. An audio frequency amplifier comprising a plurality of thermionic relays, iron core transformers for coupling said relays successively to permit of the transfer of audio frequency energy between the same, and a by-pass circuit connected directly between the anode and control electrodeof successive, relays, each circuit including therein an impedance between said relays for by-passing around the coupling between relays those audio frequencies which are ineffectively handled by the coupling means.

6. In an audio frequency amplifier, employing a plurality of vacuum tubes in cascade arrangement, coupled by transformers, a condenser in series with a resistance, connected between plate terminal of any vacuum tube and grid terminal of succeeding tube.

7. In an audio frequency amplifier system. including at least two electron discharge tubes connected in cascade by transformer coupling, a path including a condenser and resistor connected between the anode of one of the tubes and the control electrode of the succeeding tube, said resistor being adjustable for varying at will the tone value from the amplifier.

8. In an audio frequency amplifier employing vacuum tubes in cascade, a coupling arrangement between tubes comprising, in combination, transformer coupling means and resistance-condenser coupling means associated therewith, and means for bringing into predominant action either of the aforesaid coupling means. I

9. In an audio frequency amplifier employing vacuum tubes in cascade, a coupling arrangement between tubes comprising, in combination, transformer coupling means and resistance-condenser coupling means associated therewith, and means for adjusting the relative amounts of power to be passed by each.

10. In a system for amplifying currents of the audio frequency range, at least one amplifier tube,

a source of said currents, the input electrodes of said tube being connected to said source, a load adapted to utilize the amplified current output .of said tube, an audio frequency coupling network connecting the said load to the output electrodes of said tube, and an audio frequency b'y-pass path, including a resistor and condenser in series,

the relative magnitudes of said resistor and condenser being so chosen that the tone value produced from the system depends on the frequency of currents by-passed by said path, said resistor being adjustable to vary at will the said tone value.

11. In a system for amplifying currents of the audio frequency range, at least one amplifier tube, a source of said currents, the input electrodes of said tube being connected to said source, a load adapted to utilize the amplified current output of said tube, an audio frequency coupling network connecting the said load to the output electrodes of said tube, and an audio frequency by-pass path, including a resistive impedance and a condensive'impedance in series, electrically associated with said coupling network, the relative magnitudes of said resistor and condenser being so chosen that the tone value produced from the system depends on the frequency of currents by-passed by said path, at least one of said impedances being adjustable to vary at will the said tone value.

12. In a radio telephone receiver, a detector of audio modulated radio frequency currents, an audio frequency amplifier for amplifying the detected currents, said amplifier including at least one amplifier tube having its input electrodes connected to the detector output circuit, an audio frequency network, coupled to the output electrodes of said tube, for transmitting amplified audio frequency currents to the reproducer of said receiver, an aperiodic tone control impedance path electrically coupled to said network, said path including a resistor and condenser in series, and the relative magnitudes of said resistor and condenser being so chosen that the tone value of the reproduced amplified audio frequency currents depends on the audio frequencies shunted through said tone control path.

. 13. In a radio telephone receiver, a detector of audio modulated radio frequency currents, an

audio frequency amplifier for amplifying the detected currents, said amplifier including at least one amplifier tube having its input electrodesconnected to the detector output circuit, an audio frequency network, coupled-to the output electrodes of said tube, for transmitting amplified audio frequency currents to the reproducer of said receiver, an aperiodic tone control impedance path connected to the anode of said tube and being electrically coupled to said net work,-

said path including a resistor and condenser in series, and the relative magnitudes of said resistor and condenser being so chosen that the tone value of the reproduced amplified audio frequency currents depends on the audio frequencies shunted through said tone control path.

14. In a radio telephone receiver, a detector of audio modulated radio frequency currents, an audio frequency amplifier for amplifying the detected currents, said amplifier including at least one amplifier tube having its input electrodes connected to the detector output circuit an audio frequency network, coupled to the output electrodes of said tube, for transmitting amplified audio frequency currents to the reproducer of said receiver, an aperiodic tone control impedance path connected to theanode of said tube and being electrically coupled to said network, said path including a resistor and condenser in series, and the relative magnitudes of said resistor and condenser being so chosen that the tone value of the reproduced amplified audio frequency currents depends on the audio frequencies shunted through said tone control path and a second tone control path, including a resistor and condenser, connected to the input circuit of said amplifier tube.

15; In a radio telephone receiver, a detector of audio modulated radio frequency currents, an audio frequency amplifier for amplifying the detected currents, said amplifier including at least one amplifier tube having its input electrodes connected to the detector output circuit, an audio frequency network, coupled to the output electrodes of said tube, for transmitting amplified audio frequency currents to the reproducer of said receiver, an aperiodic tone control impedance path electrically coupled to said network, said path including a resistor and condenser in series, and the relative magnitudes of said resistor and condenser being so chosen that the tone value of the reproduced amplified audio frequency currents depends on the' audio frequencies shunted through said tone control path and an aperiodic tone control path, including a resistor and condenser, connected to the input circuit of said amplifier tube, and means for simultaneously adjusting the magnitudes of the resistors of both said paths.

16. In a radio telephone receiver of the type comprising a detector and a succeeding audio amplifier, the amplifier including a pair of cascaded tubes, and the last tube being adapted for connection to the receiver reproducer, a tone control device for varying at will the tone values of the reproduced amplified audio frequency currents, said device consisting solely of a resistor and condenser in series with each other, the device being electrically connected between the detector output circuit and-the input circuit of the first of said cascaded tubes, the relative values of said resistor and condenser being such that audio currents of varying frequencies may be by-passed through said device.

1'7. In a radio telephone receiver of the type including an audio frequency amplifier provided with at least one amplifier tube, a coupling means between the input circuit of said tube and the receiver circuit preceding said input circuit, the output terminals of said coupling means having a substantially higher impedance at high audio frequencies than at low audio frequencies, and an aperiodic tone control path shunted across said coupling means, said path including a resistor element and an element whose impedance value varies with applied frequencies, and means for adjusting the impedance value of one of said path elements to thereby vary the effective impedance across said terminals.

JOHN M. AVERY.

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