US2212204A - Amplifier - Google Patents

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Publication number
US2212204A
US2212204A US249221A US24922139A US2212204A US 2212204 A US2212204 A US 2212204A US 249221 A US249221 A US 249221A US 24922139 A US24922139 A US 24922139A US 2212204 A US2212204 A US 2212204A
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United States
Prior art keywords
impedance
impedances
anode
proportional
amplifier
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Expired - Lifetime
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US249221A
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English (en)
Inventor
Hepp Gerard
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RCA Corp
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RCA Corp
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Publication date
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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
    • H03F1/42—Modifications of amplifiers to extend the bandwidth
    • H03F1/48—Modifications of amplifiers to extend the bandwidth of aperiodic amplifiers
    • H03F1/50—Modifications of amplifiers to extend the bandwidth of aperiodic amplifiers with tubes only

Definitions

  • This invention relates to amplifying arrangements particularly adapted for uniform amplification of broad frequency bands including Very low frequencies.
  • Wide band amplifiers having uniform amplification or frequency-independent characteristics are of considerable importance in electrical arts, and especially in television. Hitherto, the construction of such amplifiers have been exceedingly dimcult and costly and, in many cases, could only provide uniform amplification at the cost of non-uniform time delay of signals of different frequency known as non-linear phase response characteristic.
  • This invention provides a relatively simple and cheap means of obtaining uniform amplification through a wide band of frequencies and at the same time preserving uniform phase response.
  • Another object of the invention is to provide a simple wide band amplifier having uniform amplification and time delay.
  • Fig. 1 schematically shows a single stage amplifier having embodied therein impedances chosen in accordance with my invention
  • Figs. 2, 3, 5 and 6 show modifications of the embodiment in Fig. 1 in more detail and structural elements shown in Fig. 1; while Fig. 4 shows a circuit arrangement for reducing the efiect of the stray capacity of a large condenser.
  • the frequency dependency of an amplifier is first of all determined by the frequency dependency of the coupling means provided between the individual amplifying stages, such as the impedance Z8. in the anode circuit of an amplifying tube, the impedance Z2 in the grid circuit of the succeeding tube and the coupling impedance Z1 between the anode circuit and the grid circuit.
  • the frequency-dependency of an amplifier is materially afiected by the impedance Zk which is inserted in the cathode lead for obtaininga suitable grid bias and which usually comprises a resistance and a condenser connected. in parallel therewith.
  • the screengrid lead may further include an impedance ZS which serves for smoothing the screen-grid voltage and the common lead of anode and screen grid may comprise an impedance Z (such as the internal impedance of the source of anode voltage).
  • impedance Z such as the internal impedance of the source of anode voltage
  • the present invention allows by means of such a circuit arrangement, which includes one or more frequency-dependent impedances, to obtain a frequency-independent amplification i. e. a frequency-independent ratio between the voltage 62 set up between the' output terminals A1A2 and the voltage 61 set up between the input terminals E1, E2.
  • a frequency-independent amplification i. e. a frequency-independent ratio between the voltage 62 set up between the' output terminals A1A2 and the voltage 61 set up between the input terminals E1, E2.
  • the amplifier may comprise a plurality of am- I plifying stages of the type illustrated in Fig. 1,
  • the invention allows not only of rendering each individual stage frequency-independent, but also to compensate in one stage the frequency-dependency of another stage.
  • the impedance Za in the anode-circuit and the impedance Z2 between the output terminals of the amplifying stage consist for this purpose of a resistance in series with impedances which are proportional respectively to the impedance Zk in the cathode lead, to the impedance 25 in the screen-grid lead, to the impedance Zc in the common anodeand screen-grid lead, which impedances form part of the said amplifying stage and/or of another amplifying stage, whereas the impedance Z... furthermore comprises impedances proportional to the coupling impedance Z1 in the said amplifying stage and/or in another amplifying stage.
  • the anode impedance Za consists of a resistance Ra in series with impedances ZS, flZc, 'yZk and 5Z1 which are proportional to the impedances ZS, Zc, Zr and Z1 respectively, whereas the impedance Z2 between the output terminals A1 and A2 consists of a resistance in series with impedances
  • the proportionality factors a, c, 'y and 8 must be chosen so as to fulfill the following conditions.
  • q is the ratio between the screen grid, alternating current s and the anode alternating current ia, which ratio may be considered to be constant
  • SS is the mutual conductance of the characteristic curve of the anode current/screen-grid voltage
  • S is the mutual conductance of the characteristic curve of the anode current/control-grid voltage.
  • the iinpedances Z5, Z and Z1 may, for instance comprise resistances Rs, Re, Rk together with parallel condensers Cs, Cc and Ck as shown in Fig. 3'.
  • the impedances ZS, 5Z0 and "YZk in the anode circuit must then comprise resistances ozRs, [3R0 and 'yRk together with parallel condensers and In the same manner the imp-edances 5 i i 6 7 5 Z and 6 J];
  • the coupling impedance comprises a condenser C1.
  • a condenser proportional thereto must consequently be interposed in the anode circuit. However, this blocks the direct current of the anode and must consequently be bridged by a resistance 631. Since,
  • this resistance may not be given a high value on account of the excessive voltage drop, which otherwise would be caused by the anode current and may, on the other hand, not be too small, since otherwise amplification of the low frequencies would depend on passes direct current.
  • a resistance R1 is, according to This condenser 0 must have a sufficient capacity so that its impedance may be neglected with respect to the resistance R1 even with the lowest frequencies to be amplified. To avoid that the considerable capacity with respect to earth of such a large condenser may affect the amplification of the high frequencies the resistance R1 is -preferably divided into two'par ts R between which the condenser C is connected as shown in Fig. 4.
  • circuit arrangement shown in Fig. 5 may be deduced in the following manner from the circuit arrangement shown in Fig. 2.
  • an impedance in series with Z1 a proportional impedance (l-l-q)Zc must be interposed in the anode circuit.
  • a positive impedance a proportional impedance (l-l-q)Zc.
  • the impedance which is positive for negative 5 is connected in series with Z1; in this case the impedance proportional to Z0 in the anode circuit may be entirely omitted.
  • the invention may also be used in amplifiers in which one or more of the impedances Zk, Z5 and Z0 are equal to zero.
  • the impedances proportional thereto, which are included in Za and Z2, are then also equal to zero.
  • an amplifying stage it is possible in an amplifying stage to compensate in another amplifying stage the influence of one or more of the impedances Zk, Zs, Z'c and Z1 included in the first-mentioned amplifying stage, by interposing in the impedances Z3. and Z2 of this other stage impedances proportional to Zk, Zs and Zc.
  • a wide band amplifier having uniform amplification comprising an electron discharge tube having a cathode, control electrode, screen grid and anode, a voltage supply source, a common lead, a first impedance connected between said cathode and common lead, a second impedance connected between said screen grid and a third impedance, said third impedance being connected to the common lead through the supply source, a coupling impedance connected between the anode and a first output terminal, a second output terminal connected to the common lead, an anode circuit comprising a first resistor, a fourth impedance proportional to said second impedance, a fifth impedance proportional to said third impedance, a sixth impedance proportional to said first and a seventh impedance proportional to said coupling impedance, said resistor and fourth, fifth, sixth and seventh impedances being serially connected between the anode and said third impedance, and a second resistor connected in series with a plurality of impedances proportional respectively to
  • each of the named impedances comprises a parallelly connected resistance and capacity.
  • An amplifier as claimed in claim 1 and wherein the said coupling impedance comprises connected in series in the order named a first resistor element, a first condenser element, and a second resistor element, and a second condenser connected across the serially connected elements.
  • a wide band amplifier having uniform amplification comprising an electron discharge tube having a cathode, control electrode, screen grid and anode, a voltage supply source, a common lead, a first impedance connected between said cathode and common lead, a second impedance connected between said screen grid and a third impedance, said third impedance being connected to the common lead through the supply source, a coupling impedance connected between the anode and a first output terminal, a second output terminal connected to the common lead, an anode circuit comprising a first resistor, a fourth impedance proportional to said second impedance, a fifth impedance proportional to said third impedance, a sixth impedance proportional to said first and a seventh impedance proportional to said coupling impedance, said resistor and fourth, fifth, sixth and seventh impedances being serially connected between the anode and third impedance, a second resistor connected in series with a plurality of impedances proportional respectively to said first, second

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)
US249221A 1938-01-04 1939-01-04 Amplifier Expired - Lifetime US2212204A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEP2123D DE1080610B (de) 1938-01-04 1938-01-04 Ein- oder mehrstufiger frequenz-unabhaengiger Verstaerker

Publications (1)

Publication Number Publication Date
US2212204A true US2212204A (en) 1940-08-20

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ID=7357756

Family Applications (1)

Application Number Title Priority Date Filing Date
US249221A Expired - Lifetime US2212204A (en) 1938-01-04 1939-01-04 Amplifier

Country Status (6)

Country Link
US (1) US2212204A (xx)
BE (1) BE431973A (xx)
DE (1) DE1080610B (xx)
FR (1) FR848402A (xx)
GB (1) GB510503A (xx)
NL (1) NL58853C (xx)

Also Published As

Publication number Publication date
GB510503A (en) 1939-08-02
BE431973A (xx)
FR848402A (fr) 1939-10-30
NL58853C (xx)
DE1080610B (de) 1960-04-28

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