US1795194A

US1795194A - Apparatus for amplifying electrical energy

Info

Publication number: US1795194A
Application number: US205203A
Authority: US
Inventors: Rudolph A Bierwirth
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1927-07-12
Filing date: 1927-07-12
Publication date: 1931-03-03
Anticipated expiration: 1948-03-03
Also published as: DE544807C; NL27990C; FR660695A; GB293788A

Description

Mal-id! 1931. E R. A. BIERWIRTH 1,795,194

APPARATUS FOR AMPLIFYING ELECTRICAL ENERGY Filed July 12. 1927 (III -lOO I000 IOOOO Fesousucy i/v Cyc/zs pm SECOND.

Inventor;

. Rudolph A-B i er-wirth,

His Attorney Patented Mar. 3, i931 Wires stares caries T RUDOLPH A. BI EBWIRTH, F SCHEIIECTADY, YGRK, ASSIGNOE- TO GENERAL ELEC- TRIC comrartnn GGEEGRATIGN OF NEW YORK APPARATUS FOR AMILIEYZNG ELECTRICAL ENERGY Application filed July 12,

My invention relates to apparatus for amplifying electrical energy, such as that util ized in communication systems and the like, and has for its principal object the provision of an improved apparatus and method of operation which may be utilized over a wide range of audio frequencies without substantial change in the ratio of amplification.

In the operation of the transformer or impedance coupled amplifier heretofore provided, difficulty has been encountered due to the fact that the amplification ratio varies. with frequency. In accordance with my invention, this difiiculty is avoided by the use of a coupling element whereina capacity and a plurality of inductances are so related to the other elements of the amplifier as to produce a substantially constant transformation ratio over afrequency range which ineludes low audio frequencies. I

My invention will' be better understood from the following description when considered in connection with the accompanying drawing and its scope will be pointedout in the appended claims.

Referring to the drawings, Fig. 1 shows an amplifying apparatus wherein my invention has been'embodied; and Fig. 2 relates to the operation of the apparatus shown by Fig. 1. Y

changing its transformation ratio.

1927. SerialNo. 205,203.

cuit being connected through the condenser 8 to the plate circuit of the device 4 and its secondary circuit being included in the grid circuit of the device 5. It will be apparent that the winding 7 may be replaced by a transa" former provided with separate-primary and secondary circuits and that its intermediate terminal may be ad]usted for the purpose of r In order that the amplification ratio may be maintained substantially constant over a wide range of frequencies, it is necessary that the incluctances L and L of the windings 6 and 7 and the capacity C of the condenser 8 bear a certain definite relation to the anode or plate circuit resistance R of thedevicet and the primary circuit resistance R of the This apparatus comprises input terminals 1 and output terminals 2 which are interconnected through means comprising a transformer 3, space discharge devices 4L and 5, o and'a coupling element consisting of wind-. ings 6 and 7 and a condenser 8 connected between one terminal of the winding 6 and a terminal intermediate theends of the winding '2 which may function as an auto-transformer. I

Resonance occurs when the term of the rlght hand bracket is zero. Under these conditions If L7 andzcs'al'e given the Pr per valties, the ratio the auto-translowest frequency which it is desired to amplify uniformly and this frequency is assumed to be f the ratio Substituting the value of C from Equation (2) This equation indicates that there are an infinite number of combinations of L and L which will make at w e) and C equal to the expression in Equation (2) it follows that ei-er 'Combining Equation with Equation i) and neglecting small quantities, 1t fol- For m =2w these equations give the following:

The relation between the resistance of the device 4, which may be any device having resistance without appreciable inductance the inductance 6; the capacity 8, and the resistance and reaetance of the primary circuit H 1 1 1 may be expressed as follows. The internal resistance of the device 4 plus the resistance of the primary circuit of the transformer 7 is made substantially equal to each of the reactance of the capacity 8, to the reactance of the primary circuit of transformer 7, and to one half the reactance of the inductance 6 at the lowest frequency in the range of frequencies which it is desired to amplify substantially uniformly.

Taking R; as 12000 ohms R- as 1000 ohms, f as 30 cycles, L as 150 lienries, L as 70 henries, and C as A15 microfarads, the following values of E AMEM are found for different values of frequency:

E (in percent of transformaf AME tion ratio) Fig. 2 shows the results determined experimentally with L henries, L 37 henries,

tl =l microfarad, f =27 cycles, R =5100, and a 1 to 4r transformer ratio. It will be observed that between 30 and 7000 cycles there is a variation in the ratio 05 AME of only about three percent. This shows that the amplification ratio of the apparatus is substantially constant throughout the entire audio frequency range.

It will be noted that the calculated Values are slightly higher than the experimentally determined values at the low frequency end of the curve. This difference is due to the core loss which was not taken into consideration in the calculation. In the apparatus used to secure the data on which the curve is based, the flux density was comparatively high for an interstage transformer. is kept low, the core less effect is practically negligible and the conditions under which substantially constant transformation ratio over a wide range of frequencies is possible can be readily determined from equations (8), (9) and (10).

The embodiment of the invention illustrated and described herein has been selected for the purpose of clearly setting forth the 3-:1

principles involved. It will be apparent, however, that the invention is susceptible of being modified to meet the diiferent conditions encountered in its use andI therefore aim to cover by the appended claims all mod- If the flux density T if ifications within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an audio frequency amplifier, the combination of a space discharge deviCeprovided with an anode circuit, an inductance connected in said'circuit, a capacity, and a transformer provided with a primary circuit connected to said anode circuit through said capacity, the internal resistance of the space discharge device plus the resistance of the primary circuit of the transformer being substantially equal to each of the reactance of the capacity, to the reactance of the primary circuit, and to one half the reactance of the inductance at the lowest frequency in the range of audio frequencies which it is desired to amplify substantially uniformly. p

2. In an audio frequency amplifier, the combination of a pair of space discharge devices each provided with an input and an output circuit, an inductance connected in theoutput circuit of one of said devices, a capacity, and a transformer provided with a primary circuit connected to said output circuit through said capacity and with a secondary circuit connected in the input circuit of the other of said devices, the internal resistance of said one of said devices plus that.

of said primary circuit being substantially equal to the reactance of said capacity, to each of the reactance of said primary circuit, and to one half the reactance of the inductance at the lowest frequency in the range of audio frequencies whichit is desired to amplify substantially uniformly.

3. An audio frequency amplifying apparatus including a space discharge device provided with an anode circuit, an inductance connectedin said anode circuit, a capacity, and a transformer provided with a primary circuit connected to said anode circuit through said capacity, the magnitudeof said" inductance in henries being substantially equal to .373 times the resistance of said anode circuit in ohms divided by the lowest audio frequency in cycles per second which it is desired to amplify.

4. An audio. frequency amplifying apparatus including a space discharge device provided with an anode circuit, an inductance connected in said anode circuit, a capacity,. r and a transformer provided with a prlmary circuit connected to said anode circuit through said capacity, the inductance of said primary circuit in henries being substantially equal to the lowest audio frequency in cycles per second that it is desired to amplify di- 1 vided into the sum of 159 times the res1st-= ance of said anode circuit in ohms and .188 times the resistance of said primary circuit in ohms. i

5. An audio frequencyiamplifying apparatus including aspace discharge device provided with an anodecircuit, an inductance connected in said anode circuit, a capacity, and a transformer provided with a prlmarycircuit connected to 'said anode circuit m through said capacity, the magnitude of said capacity in microfarads being substantially equal to the quotient obtained by dividing .159 by the product of the lowest audio frequency in cycles per second which it is de sired to amplify and the sum of the resistance of said anode circuit 111 ohms and .75 times the resistance" of said primary circuit in vice in ohms'and inversely proportional to the lowest frequency which it is desired to transmit through said element. 7

7. In an audio frequency amplifier, a device for the transmission of audio frequency currents having a certain internal resistance, an output circuit therefor, a capacity, and an audiofrequency transformer having a primary circuit connected with said output circuit through said capacity, the reactances of said capacity and of said primary circuit at the lowest frequency in the range of audio frequencies which it is desired to amplify substantially uniformly being substantially:

equal to each other and to the internal resistance of said device plus that of the primary circuit. I

8. In an audio frequency amplifier, a dev ce for the transmlssion of audio frequency currents having a certain internal resistance,

an output circuit therefor, a capacity,an-

audio frequency transformer having a pri- 'mary circuit connected with said output circuit through said capacity, the reactances of said capacity and of said primary circuit at ance of said device plus that of the primary circuit, and'means for supplying currentto said output circuit including an impedance having a reactance at said lowest audio frequency greater than that of said primary clrcuit.

9. An audio frequency amplifying apparatus including a space discharge device provided with an anode circuit, an inductance connected in said anode circuit, a capacity, and a transformer provided with a primary circuit connected to said anode circuit through said capacity, the magnitude of said inductance in henries being substantially equal to .373 times the resistance of said anode circuit in ohms divided by the lowest audio frequency in cycles per second Which it is desired to amplify, the inductance of said primary circuit in henries being substantially equal to the lowest audio frequency in cycles per second that it is desired to amplify divided into the sum of .159 times the resistance of said anode circuit in ohms and .188

times the resistance of said primary circuit in ohms, and the magnitude of said capacity in microfarads being substantially equal to the quotient obtained by dlvlding .159 loy the product of the lowest audio frequency in cycles per second which it is desired to amplify and the sum of the resistance of said anode circuit in ohms and .75 times the resistance of said primary circuit in ohms.

In Witness Wl1I-'60f,-I have hereunto set my hand this 11th day of July, 1927.

RUDOLPH A. B'IERWIRTH'.

- Certificate of Correction Patent No.1,795,194. g Granted March 3, 1931, to RUDOLPH A. BIERWIRTH It is hereby certified that error appears in the printed specification of the abovenumbered patent requiring correction as follows: Page 2, line 30, for u =w read co =w same page at the beginning of equation 7 between lines 45 and 50, for L m read L =i and that the said Letters Patent should be read with these correctionstherein that the same may conform to the re cord of the casein the Patent Oflice.

Signed and sealed this 31st day of March, A. D. 1931.

[SEAL] M. J. MOORE,

Acting Commissioner of Patents.