US2373534A - Low frequency amplifier - Google Patents

Low frequency amplifier Download PDF

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Publication number
US2373534A
US2373534A US157078A US15707837A US2373534A US 2373534 A US2373534 A US 2373534A US 157078 A US157078 A US 157078A US 15707837 A US15707837 A US 15707837A US 2373534 A US2373534 A US 2373534A
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United States
Prior art keywords
resistance
circuit
valve
input
coupling
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Expired - Lifetime
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US157078A
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English (en)
Inventor
Broos Henricus Adrianus
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RCA Corp
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RCA Corp
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Publication date
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Publication of US2373534A publication Critical patent/US2373534A/en
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/34—Negative-feedback-circuit arrangements with or without positive feedback
    • H03F1/36—Negative-feedback-circuit arrangements with or without positive feedback in discharge-tube amplifiers

Definitions

  • FIG. 2 shows an amplifier employing separate controls for amplifier input and positive feedback respectively
  • Fig. 2 a modification of the circuit of Fig. 1 in which negative feedback is employed
  • Fig. 3 is a further modification wherein a single control is used for amplifier input, negative feedback and positive feedback
  • Fig. 4 shows a modification with common control for amplifier input and negative feedback and a separate control over the low frequency feedback
  • Fig. 5 is a further modification of ,the circuit shown in Fig. 4;
  • Fig. 6 is a modification of the circuit of Fig. 3 applied to a push-pull output stage.
  • the penultimate tube of a low frequency amplifier is denoted by I and the terminal valve by 2.
  • the anode circuit of the valve 2 comprises the primary winding'of a transformer 3 whose secondary winding is connected to a loudspeaker.
  • the arrangement is adapted both for receiving purposes and for record reproduction. Changing-over is effected by means of the switch 4.
  • I2 is a tuned circuit which is preferably coupled to the final stage of the intermediate frequency amplifier of a receiving set.
  • the voltages occurring thereover are rectified by a detector diode incorporated in the valve I.
  • a pick-up is denoted by II.
  • the rectified signals are supplied 4 Claims. (01.
  • Pig. 2 shows a circuit arrangement which substantially corresponds to that represented in Fig. l, but in whichthe electrode of the condenser 8 gal I fective for the lower frequen 2 connected to an adjustable point III of the resistance 9 forming part of the grid circuit of the valve I.
  • a negative backcoupling is obtained which is particularly effective for high frequencies, and is practically zero for low frequencies.
  • the amplifying characteristic can still be improved.
  • the sound strength can be controlled by shifting the contact on the resistance 5
  • the degree of back-coupling can be controlled by shifting the contact III on the resistance 9.
  • Fig. 3 represents a circuit arrangement in which the quality is controlled automatically in accordance with the'sound strength.
  • the signals to be amplified are supplied to a resistance I3 one of whose ends is earthed, whereas the other end is connected to the upper end of the resistance 5.
  • the complete back-coupling is operativ'in the input circuit of the valve I.. In this ic'ase the sound strength is minimum. Theratiolbetween the strength of the low sounds, and. thatof the high sounds is maximum which is jus desired. when the said contact is in its upperjposition the negative back-coupling is a whereas the positive back-coupling which?
  • Figure 4 represents anarrangement according to the invention, in which the final stage comprises two push-pull connected valves H and 15.
  • the output voltage of the two terminal valves should be coupled back, which is effected by connecting the cathodes across resistances l8 and "Is to the resistances I8 and ll.
  • These last-mentioned resistances form part of the input circuit of .the valve I.
  • the common point of these resistances is earthed.
  • a simple consideration shows that in this manner the two voltages are coupled back in the suitable-phase if the polarity of transformer 20 is correctly chosen, as must be determined by the method of trial and error;
  • the cathodes are connected through a condenser 2
  • the ratio between the higher and the lower frequencies in the output circuit can be controlled by means'of a resistance -22 connected in parallel with the resistances i and i! or in parallel with C21.
  • Fig. 5 shows a circuit arrangement which comprises, moreover, a negative back-coupling for the high frequencies. This is effected through the condensers 23 and 24 connected between the cathode of the valve and the cathode of the valve l, and between the cathode of the valve l4 and the bdttom end of the resistance i! respectively.
  • the back-coupling can be controlled bymeans of a variable resistance 25-which is interposed between the two cathodes, but may also be connected parallel with the resistances it and H.
  • Figs; 4 and 5 is illustrated, moreover, how'tiie back-coupling can be rendered dependent on the sliding contact on the resistance 5.
  • Fig. 5 exactly the same control of feedback results from the movement of the slider to resistance 5, since the source of feedback voltage is connected on the one hand directly to the cathode of the'ilrst' tube and on the. other hand through the same arrangement,
  • Fig. 6 represents a circuit arrangement comprising a. negative back-coupling only for the higher frequencies in the grid circuit of the valve I across'the resistances l6 and I1. back-coupling for the low frequencies is not provided in this arrangement.
  • an audio amplifier having an audio input circuit and an audio output circuit, said input circuit including an impedance across which is developed audio signal voltage, a resistive path in shunt with said impedance, 9. degenerative signal voltage feedback path connected between said output circuit and an intermediate point of said rean adjustable connection between the input electrode of said amplifier and a portion of said path between one endthereof and said point, said amplifier including at least two cascad tubes each having a cathode] input electr and anode, and resistive means connecting the oathodes of both tubes in common to the opposite end of said shunt resistive path.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)
US157078A 1936-08-03 1937-08-03 Low frequency amplifier Expired - Lifetime US2373534A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2373534X 1936-08-03

Publications (1)

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US2373534A true US2373534A (en) 1945-04-10

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ID=7995588

Family Applications (1)

Application Number Title Priority Date Filing Date
US157078A Expired - Lifetime US2373534A (en) 1936-08-03 1937-08-03 Low frequency amplifier

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US (1) US2373534A (enrdf_load_stackoverflow)
BE (1) BE422932A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2543462A (en) * 1945-10-19 1951-02-27 Conrad L Longmire Pulse equalizer

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2543462A (en) * 1945-10-19 1951-02-27 Conrad L Longmire Pulse equalizer

Also Published As

Publication number Publication date
BE422932A (enrdf_load_stackoverflow)

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