US2290553A - Negative feedback circuit arrangement - Google Patents

Negative feedback circuit arrangement Download PDF

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Publication number
US2290553A
US2290553A US374066A US37406641A US2290553A US 2290553 A US2290553 A US 2290553A US 374066 A US374066 A US 374066A US 37406641 A US37406641 A US 37406641A US 2290553 A US2290553 A US 2290553A
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Prior art keywords
circuit
amplifier
diode
modulation
amplitude
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US374066A
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English (en)
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Haantjes Johan
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Individual
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Individual
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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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C1/00—Amplitude modulation
    • H03C1/02—Details
    • H03C1/06—Modifications of modulator to reduce distortion, e.g. by feedback, and clearly applicable to more than one type of modulator

Definitions

  • This invention relates to a circuit arrangement for transmitting amplitude-modulated oscillations through at least one amplifier.
  • the invention has for its object to utilize in such circuits negative feed-back for the modu- It has already been suggested to establish negative feed-back for the modulation frequencies by detecting the output voltage of the amplifier for amplitude-modulated oscillations and by modulating again the modulation-frequencies latter being tuned to the frequency of the am- This oscillatory plitude-modulated oscillations.
  • circuit is disposed in the input circuit of the amplifier in such manner that the applied bias becomes more positive with an increasing carrier wave amplitude.
  • the diode acting as a modulator involves amplitude modulation in the oscillatory input circuit, which modulation is additiveiy composed of the amplitude modulation already available and the detected voltage carried back.
  • Fig. 2 shows an application of the invention to a radio transmitter
  • Fig. 3 shows howit is in a radio reoscillatory circuit 4.
  • a diode 5 having a load resistance is connected to the oscillatory circuit 4.
  • This load resistance consists of two seriesconnected resistances 6 and 1.
  • a condenser 8 In parallel withthe resistances Band I is connected a condenser 8 which has 'a' negligibly small impedance to wards the amplitude-modulated oscillations.
  • diode 9 having a load resistance is connected in parallel with the oscillatory circuit i inthe input circuit of the amplifier 2.
  • This load resistance consists of the resistance I and a resistance ill connectedin series.
  • a condenser H having a low impedance for the .oscillations to be amplified. Jhcoperation of this circuit is as follows:
  • the f amplitude-modulated oscillations are produced in a modulator 12 to which are supplied nonmodulated oscillations by an oscillator I3, and modulation frequencies by a low frequency amplifier I l.
  • the amplitude-modulated oscillations are transmitted to the oscillatory circuit l by an oscillatory circuit I5 connected to-the modulator l2.
  • the load connected to the oscillatory circuit 3 is constituted by a transmitting antenna I! which is inductively coupled with the circuit 3 through a coil [6.
  • Fig. 3 the circuit arrangement shown in Fig. 1 is used in a radio receiver where the intermediate frequency amplifier, and in addition the lowfrequency amplifier of the receiver, is back-coupled in a degenerative manner.
  • the oscillations picked up by means of an antenna l8 are amplified in a high frequency am-- plifier l9 and jointly with locally generated oscillations of an oscillator supplied to a mixing stage 2l.
  • the intermediate frequency amplitude-modulated oscillations produced herein are amplifiedin an intermediate frequency amplifier 22 and subsequently detected by a second detector 23, whereupon the low frequency oscillations produced herein are-amplified by a low frequency amplifier 24 and supplied through transformer 25 to a loud speaker 26.
  • the input circuit of the intermediate frequency amplifier 22 similarly to Fig. 1 includesan oscillatory circuit I, a diode 9, a condenser II and a resistance 10.
  • One of these voltages is a direct voltage which is a measure of the intensity of the intermediate frequency carrier wave and is produced by detection in the second detector 23 and diverted therefrom to ground by way of a potentiometer 28. A part of the voltage across this potentiometer is supplied in series with a low 1. In a discharge tube amplifier and circuit.
  • This low frequency voltage is taken from the secondary winding of transformer 25 and, through a potentiometer 29 and a phase shifting device 30, connected in series with the direct voltage through part of the potentiometer 28.
  • the potentiometer 29 permits adjustment of the correct value of the various components of the low frequency voltage, while the phase shifting device 30 allows adjustment of their phase.
  • frequency dependent phase displace-- merit occurs in the intermediate frequency amplifier and in the low frequency amplifier, which displacement must be corrected prior to backcoupling ina degenerative manner.
  • Negative feed-back of the whole receiver might be achieved by connecting the diode 9 to the input'oscillatory circuit of the high frequency amplifier l9. In this case, however, the drawback occurs that the incoming signal voltage is therectified modulation component upon the energy shunted through said variable unilateral impedance, thereby to produce a negative feedback effect upon said input circuit.
  • the circuit of said variable unilateral impedance includes a diode rectifier and a potentiometer a portion of which is in circuit with said means for rectifying a modulation component of the output energy.
  • a circuit arrangement for translating amplitude modulated oscillations including an amplifier, a resonant input circuit for said ampliportion of said input circuit, an electronic detector coupled to the output side of said amplifier, a resistive. impedance interconnecting the respective cathodes of said rectifier and said detector, a direct current connection from the oathode of said diode to ground, a resistive feedback circuit from the anode of said detector to an intermediate tap on the resistive impedance first mentioned, and capacitive means for dissipating unwanted alternating potential components in said input and output circuits; said diode rectifier and said feedback circuit being cooperative to produce a variable damping effect on said amplifier which is 'a function of the amplitude of said modulated oscillations.
  • a circuit arrangement for receiving amplitude modulated oscillations including at least .one amplifier, a resonant input circuit for said amplifier, a diode rectifier in shunt with the resonant portion of said input circuit, a detector coupled the output side of said amplifier, a utilization device having an input circuit and means coupling the same to said detector, a feedback circuit connected to the coupling means between said detector and said utilization device,

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)
US374066A 1939-09-26 1941-01-11 Negative feedback circuit arrangement Expired - Lifetime US2290553A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL2290553X 1939-09-26

Publications (1)

Publication Number Publication Date
US2290553A true US2290553A (en) 1942-07-21

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ID=19874034

Family Applications (1)

Application Number Title Priority Date Filing Date
US374066A Expired - Lifetime US2290553A (en) 1939-09-26 1941-01-11 Negative feedback circuit arrangement

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US (1) US2290553A (is")
FR (1) FR872843A (is")
NL (1) NL58860C (is")

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2446025A (en) * 1946-05-10 1948-07-27 Avco Mfg Corp Modulation system
US2512637A (en) * 1945-08-10 1950-06-27 Us Sec War Noise suppression circuit
US2607888A (en) * 1944-07-24 1952-08-19 Cossor Ltd A C Radio signal discriminating apparatus
US2692377A (en) * 1946-01-16 1954-10-19 Jr George A Brettell Position plotter
US2894123A (en) * 1953-12-31 1959-07-07 Rca Corp Radio transmitter with fixed tune amplifier stages

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2607888A (en) * 1944-07-24 1952-08-19 Cossor Ltd A C Radio signal discriminating apparatus
US2512637A (en) * 1945-08-10 1950-06-27 Us Sec War Noise suppression circuit
US2692377A (en) * 1946-01-16 1954-10-19 Jr George A Brettell Position plotter
US2446025A (en) * 1946-05-10 1948-07-27 Avco Mfg Corp Modulation system
US2894123A (en) * 1953-12-31 1959-07-07 Rca Corp Radio transmitter with fixed tune amplifier stages

Also Published As

Publication number Publication date
FR872843A (fr) 1942-06-19
NL58860C (is")

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