US2273656A - Amplifier control circuits - Google Patents

Amplifier control circuits Download PDF

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Publication number
US2273656A
US2273656A US322461A US32246140A US2273656A US 2273656 A US2273656 A US 2273656A US 322461 A US322461 A US 322461A US 32246140 A US32246140 A US 32246140A US 2273656 A US2273656 A US 2273656A
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United States
Prior art keywords
tube
capacity
circuit
input
amplification
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Expired - Lifetime
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US322461A
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English (en)
Inventor
Oosterhuis Ekko
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RCA Corp
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RCA Corp
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Publication date
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Publication of US2273656A publication Critical patent/US2273656A/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
    • H03F1/08—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements
    • C—CHEMISTRY; METALLURGY
    • C06—EXPLOSIVES; MATCHES
    • C06F—MATCHES; MANUFACTURE OF MATCHES
    • C06F5/00—Matches

Definitions

  • This invention relates to a circuit arrangement for the transmission of electrical oscillations .which includes at least one electron discharge tube and means for controlling the amplification thereof by a control voltage which acts upon the tube.
  • a control voltage is usually applied to the input grid of the tube and by which voltage the working slope of the grid voltage-anode current characteristic is acted upon in a desired manner.
  • control circuits that, simultaneously with the desired amplification variation, there occur considerable variations of the working capacity between the various connecting points, more particularly between the grid and the cathode of the tube.
  • Such'variations give rise to detuning of the connected oscillatory circuits if the order of magnitude of capacity of the oscillatory circult can be compared with that of the capacityvariations of the tube.
  • the input capacity of the tube between the control grid and the cathode may in many cases vary by 1.5 mmf, With a capacity of the oscillatory circuit,of 75 mmf., the value of the detuning involved thereby may amount to-about 1% of the In the circuit arrangement shown in Fig. 1 the signal oscillations to be amplified, which are applied to the terminals of an oscillatory circuit l,
  • Amplification control of tube 4 is effected "by supplying a control voltage to the signal grid 3 through a resistance 5.
  • the amplified oscillations are supplied to an in- It has been found maining part of the circuit arrangement (not ductance 6 disposed in the anode circuit of tube 4, and with which inductanceis coupled the rerepresented in the drawing).
  • the control voltage required for controlling the amplification of tube 4 is taken from a resistance 8 in the cathode lead of tube 4.
  • the resistance 8 is furnished with a sliding contact I and is bridged by a condenser 9 having a negligible impedance for alternating currents of the frequency to be amplified.
  • the present invention permits the said variations of the working capacity to be avoided in controlling the amplification.
  • the variations in capacity'caused by this end a fixed resistance is preferably con- 5 nected in series with the variable condenser.
  • Fig. 1 represents a circuit arrangement in -which amplification is controlled manually and the correcting condenser is operated at the same time, 1 1
  • Fig. 2 shows a circuit arrangement wherein control of amplification and'the correcting condenser is efiected automatically
  • variable condenser I0 is connected between the signal grid 3 of tube 4 and the grounded electrode of condenser 9.
  • This variable condenser I0 is mechanically connected to the sliding contact 1 of *resistance 8, The mechanical coupling is indicated by a dotted line H.
  • Fig. 2 the amplification of tube 4 is not controlled manually but automatically.
  • the signal grid 3 is connected through the resistance 5 to a lead 12 which is connected to a signal rectifier for automatic volume control (not represented).
  • AVC designate the connection to a usual automatic volume control rectifier. During am-- ,plification control the input capacity and at the same time the anode direct current of tube 4 vary.
  • the anode circuit includes a galvanometer device I3 which is mechanically coupled with the variable condenser ID for compensation of the input capacity, and which mechanical coupling is indicated by a dotted line I4.
  • variable condenser I In order to make up for the decreasinginput capacity of tube 4 the variable condenser I is controlled by the galvanom-- eter device in such a manner that the capacity increases.
  • the resistance I5 connected in series with the variable condenser l0 exerts a damping effect on the oscillatory circuit, and which damping increases with increasing negative bias and makes up for the damping which is exerted by tube 4 on the oscillatory circuit I and decreases with increasing by the capacity existing between said control electrode and cathode varies, a device connected between said input terminals providing a compensating 'capacity'thereacross, and means conjointly operative with changes in said potential difference for varying the magnitude of said compensating capacity in a sense to prevent said first capacity from being efiective across said input terminalsand a resistor in series with said device whose damping efiect between said input terminals increases wtih increase of the compensating capacity magnitude.
  • said improvement comprising an adjustable capacitance device operatively associated with said input circuit to oppose the effect of said component, and means for controlling said device in response to operation of said bias varying means .and in a sense to compensate for variations in the magnitude of said component said device having a resistor of predetermined value in series therewith across said input circuit, and said resistor compensating for variations in the resistive component of said impedance.
  • a signal amplifier of the type having a resonant input circuit said amplifier comprising a tube having at least a signal grid, cathode and output electrode, means for varying the bias of said grid over a range such that the inherent tube grid to cathode impedance veriation afiects the input circuit response characteristic, means connected in shunt across said input circuit for providing a compensatory impedance thereacross, and means for control of said shunt means in response to said varying means, said inherent impedance having a capacity component and a resistive component, and said shunt means including an adjustable capacity in series with a resistor whose damping effect on said input circuit increases with increase of magnitude of said adjustable capacity.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Amplifiers (AREA)
US322461A 1939-07-11 1940-03-06 Amplifier control circuits Expired - Lifetime US2273656A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL94284A NL54973C (enrdf_load_stackoverflow) 1939-07-11 1939-07-11

Publications (1)

Publication Number Publication Date
US2273656A true US2273656A (en) 1942-02-17

Family

ID=42830123

Family Applications (1)

Application Number Title Priority Date Filing Date
US322461A Expired - Lifetime US2273656A (en) 1939-07-11 1940-03-06 Amplifier control circuits

Country Status (3)

Country Link
US (1) US2273656A (enrdf_load_stackoverflow)
FR (1) FR872091A (enrdf_load_stackoverflow)
NL (1) NL54973C (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2577746A (en) * 1944-11-11 1951-12-11 William R Faust Variable reactance decoupling circuit

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2577746A (en) * 1944-11-11 1951-12-11 William R Faust Variable reactance decoupling circuit

Also Published As

Publication number Publication date
NL54973C (enrdf_load_stackoverflow) 1943-07-15
FR872091A (fr) 1942-05-29

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