US2524821A - Wide frequency band amplifier - Google Patents

Wide frequency band amplifier Download PDF

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Publication number
US2524821A
US2524821A US581098A US58109845A US2524821A US 2524821 A US2524821 A US 2524821A US 581098 A US581098 A US 581098A US 58109845 A US58109845 A US 58109845A US 2524821 A US2524821 A US 2524821A
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United States
Prior art keywords
filter
anode
valve
cathode
grid
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Expired - Lifetime
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US581098A
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English (en)
Inventor
Montgomery William Alan
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International Standard Electric Corp
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International Standard Electric Corp
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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/0138—Electrical filters or coupling circuits
    • H03H7/0146—Coupling circuits between two tubes, not otherwise provided for
    • 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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/54—Amplifiers using transit-time effect in tubes or semiconductor devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/17—Structural details of sub-circuits of frequency selective networks
    • H03H7/1741—Comprising typical LC combinations, irrespective of presence and location of additional resistors
    • H03H7/1775—Parallel LC in shunt or branch path

Definitions

  • the present invention relates to multi-stage amplifiers employing thermionic valves of the grounded-grid type and is concerned with the interstage coupling arrangements for such amplifiers, particularly those designed for use at ultra-high frequencies.
  • the valves are of the kind intended to be operated with the control grid connected to earth, or at least maintained at earth potential for the signal waves.
  • the input signal voltages are therefore applied to the cathode, and the-output voltages are taken between the anode and control grid.
  • the valve operated iri this way has a very low input impedance, and the reactances associated with the output circuits of the valves may have a controlling inuence on the coupling arrangements of two successive stages.
  • the coupling arrangements since the input impedance of the valve is low, the coupling arrangements must full certain definite conditions if maximum gain over the transmitted band is to be obtained, which conditions are quite different from those which apply when the valves are operated in the usual way.
  • the principal object of the present invention is to provide an eicient coupling network for two stages of a grounded-grid valve amplifier intended to pass a specified band of frequencies. While the frequencies of special interest to the invention are in the ultra-high-frequency range, the same principles are applicable in other ranges. y
  • an electric wave amplifier comprising two thermionic valves having their control grids connected to ground. and a network connecting the anode of the first of the said valves to the cathode of the second valve, the said network being so designed that when combined with the inter-electrode capacities of the valves it constitutes a transforming filter adapted to pass a frequency band of specified width, the output image admittance of the said filter at the mid-band frequency being equal to the conductance component of the cathode-control grid admittance of the'said second valve at that frequency, when the anode of that valve is connected to a network similar to the said network or to an equivalent load.
  • the invention also provides an electric wave amplifier comprising two thermionic valves having their control grids connected to earth, a system of hollow metal tubes enclosing the said valves and having central conductors connected in such a manner as to form with the inter-electrode capacities of the said valves a transforming iilter for coupling the anode of one valve to the cathode of the other valve, the said filter being adapted to pass a band of frequencies of specified width, and having an outputiimage admittance at the mid-band frequency equal to the conductance component of the cathode-control grid admittance at that frequency of the said other valve when the anode of that valve is loaded by a similar transforming filter, or by an equivalent load.
  • Fig. l shows a schematic circuit diagram showing two grounded grid valves coupled by an arrangement according to the invention
  • Figs. 2 to 6 show circuit diagrams of lters to show how a transforming filter according to the invention may beevolved
  • Fig. 7 shows a schematic circuit diagram of two stages of an amplier employing a lter according to Fig. 6;
  • Fig. 8 shows an alternative configuration for the transforming filter
  • Fig. 9 shows a schematic circuit diagram of two stages of an amplifier employing a filter according to Fig. 8.
  • Fig. l() shows an embodiment of an amplifier employing a filter having the configuration of Fig. 5.
  • Figure l1 shows another embodiment employing a filter having the configuration of Figure 6.
  • the invention is not restricted to amplifiers employing simple grounded-grid triodes only.
  • the valves may be of special types, such as beam tetrodes or aligned-grid tetrodes, provided always that the control grid is earthed.
  • triode valves having three parallel plane electrodes specially designed for ultra-high frequencies are of particular interest in connection with the present invention. Such valves are described, for example, in the specification of U. S. Patent No. 2,419,544.
  • the reactances associated with the input and output circuits of the valve, and with the connection leads must be taken into account and may be controlling factors, and ⁇ it has been found that these reactances ,can be utilised to form the elements or parts of the elements of a band-pass coupling filter designed to pass with a minimum of distortion a certain band of frequencies.
  • the input impedance of a grounded grid valve is rather low, and therefore in order to obtain a coupling which operates with maximum eiiiciency, the coupling filter should include the equivalent of a step-down transformer. In other words, an impedance transforming filter iS required.
  • C components of the anode-cathode and control grid-cathode votages, and z' is the corresponding instantaneous value of the A. C. cornponent of the anode current.
  • Z1 measured between the cathode and control grid is given by:
  • Zt is the external load impedance connected between the anode and control grid of the valve. This is on the assumption that there is no grid current, that the anode-cathode capacity of the valve is negligible, and that the cathodecontrol grid and anode-control grid capacities C1 and Ci are considered as'parts of the external circuitsconnected to the valve.
  • Fig. 1 shows in block schematic form a circuit according to the invention.
  • two simiar grounded grid valves V1 and V2 coupled by a network N of reactive elements which together with the Valve capacites Ct and C1 forms a transforming filter TF.
  • This filter is terminated on its output side by the impedance Z1, and Zt is the impedance measured at its input terminals when so terminated.
  • the capacities Ct and C1 are treated as though they formed part of they coupling filter TF. These capacities will be taken to include any additional stray capacities introduced by leads, and the like, which will, of course, be reduced to a rilinimum. They will therefore be neglected for the present when considering the action of the valves, which will thus be assumed not to have any capacities associated with them.
  • the design of the filter TF' will be treated rst of all in terms of the mid-band angular frequency wo which is equal to Van-wz, where w1 and wz are the two cut-ofi angular frequencies.
  • Equation 1 From Equation 1 it can be seen that Z1 is real if Zt is real, and vice-versa. Let it be assumed that Z1 is real vand equal to R1.
  • the coupling filter TF will be designed according to the invention so that its output image impedance at wo is R1. Then its inout image impedance will be R1/n2 where n is 1ess than 1 and is the transformation ratio of the equivalent'steri-down transformer effectively contained in the filter. Thus and is real, so that the condition of Equation 1 is satisfied.
  • Equation 1 we have 'I'hus G increases as Re increases, and the maximum theoretical value of G is therefore ,1+1, but only much smaller values are usually possible for reasons which will a-ppear later.
  • the input characteristic impedance of the filter is Rt, and it will be properly terminated by the impedance R1 connected on the other side of the transformer.
  • R1 is provided by the input circuit of the valve V2, from which circuit the capacity C1 has been removed and considered as part of the filter.
  • the admittance l/R1 is the same as the conductance component of the admittance of the input circuit of the valve, which admittance could, of course, only be measured with the capacity C1 present.
  • l/Rt is the input image admittance of the filter, it would most probably be measured as the conductance component of the admittance looking into the input side of the network N (Fig. 1) but the capacity Ct could be included by making the measurement with the valve V1 in position, but with the heater switched off.
  • C2 is first taken equal to Ct, the anode grid capacity of the valve together with the capacity of any Aleads attached thereto.
  • the speciiied band Width wz-wl then determines Rt from Equation 6.
  • the inductances L1 and Le are then determined from Equations 4 and 5 by inserting the specified values of w1 and wz. Having determined the -value of n then L5, Lv and La are found from the Equations '7.
  • Equation 2 It will be seen from Equation 2 that n is fixed by the choice of the valve, when Rt has been determined; thus it may sometimes be found that La is negative and therefore unrealisable. This means that with this particular type of filter designed in the manner explained, when the band Awid-th is specified, the mid-band angular frequency wo cannot be below a certain minimum value, though it can be above. This is not a serious disadvantage in some amplifiers, because that La is infinite, and is'therefore omitted altogether. The filter then reduces to the form shown in Fig. v6. This requires that:
  • L2 nLi/(1n) (8i From Equations 4, 5 and 8, it then follows that I'his determines w1 and wz separately since the bandwidth u2-w1 is given, and the values of L1 and Lz are then found from Equations 4 and 5, and thence L5 and L7 from Equations '7.
  • C3 is about ve times C1, so that an additional capacity of about 14.6 micro-microfarads must be connected across the output of the filter TF.
  • th'e filter has so far been based upon consideration of the mid ⁇ -band angular frequency wo at which the filter has an image impedance which is a pure resistance, and the filter can be and is terminated correctly by a pure resistance at this frequency. These conditions do not generally hold at other frequencies in the pass band when the filterv is so terminated, and the gain calculated from the simple formula G--1/n2 does not generally hold at other frequencies. It can, however, be shown that for the type of filter shown in Figs. 2 to 6, the gain at w1 and wz is the same as that at wu', but between wi and wo and between wo and wz the gain is generally a little higher, there being two unequal maxima, one on either side of wo. It is however, unlikely that the maximum gain in any Apart of the band will be more than about 1.6 db. above the gain at wo.
  • the gain per stage which it is possible to obtain is in effect limited by the characteristics of the valve chosen, and varies opfpositely with the band width; thus wider bands imply lower gain.
  • the available gain per stage is greater when R and Ct are smaller.
  • the valve should have high values of ,L and low values of Ct and R.
  • Fig. 7 is a schematic circuit diagram to show how the coupling filter of Fig. 6 may be applied in practice.
  • the capacities C1 and Ct associated with the valves are shown dotted in order to indicate that they do not represent any actual circuit elements.
  • the condensers designated K are bypass condensers of relatively large capacity so that their reactance at the operating frequency is negligible.
  • the anode of V1 is connected to the cathode of V2 through the coil L5 and a blocking condenser H.
  • Anode potential is supplied to the anode of V1 through the shunt coil I nand through L5, the coil Inbeing effectively connected to earth through the bypass condenser K.
  • the variable condensers Qt and Q1 are connected in parallel with C1. and C1 and enable the desired values of the filter capacities Cz and Ca to be obtained in the manner described.
  • Q1 is preferably a very small condenser having a range just suicient to cover the maximum variation of C1.
  • the cathode heaters are supplied from separate heating sources HSI and HS2 through choke coils Lh'having a very high impedance at the operating frequency in order to prevent the heating source from short circuiting the filter. These coils together with the corresponding bypass condensers K also prevent coupling between the stages through the heating sources. Cathode bias is provided by the resistances Rb.
  • the inductances L5 and L1 may consist of simple solenoids of a few turns and should be placed with their axes at right angles and not too near together in order to avoid any appreciable mutual inductance which would modify the action of the lter.
  • the coils L11 may also be solenoids not too closely wound in order to reduce the self capacity.
  • Each of the condensers K can usually be provided by means of a small plate fixed to the screen of the amplifier and insulated therefrom by a sheet of mica or the like.
  • Qt and Q1 can be small rotary air condensers of conventional type. y
  • the filter according to Fig. 5 may be constru-cted in another way. It is well known that the network of the three inductances L5, In and La is equivalent to a two-winding transformer. This figure can therefore be redrawn as Fig. 8, in which In and L are the inductances of the two transformer windings, and M is the mutual inductance between them.
  • Two side tubes 3 and 4 are provided, the central conductor of tube 3 being connected to the anode end of conductor 2 and passing out of the tube 3 at the closed end.
  • a plate 6 insulated from the end of the tube forms a bypass condenser.
  • the conductor 5 is connected to the anode supply source.
  • the central conductor of the tube 4 is a tube 1 connected to the cathode end of the conductor 2, and the second heater conductor 'B passes through this tube and out through theclosed end of the tube 4.
  • a flange 9 attached to the tube 'I forms the necessary bypass condenser, and a lead I0 connected to the flange 9 also passes outside the tube 4.
  • Leads 8 and I8 are connected to the cathode heatingr source HS.
  • the condensers Qt and Qi are supplied as before, and are connected between the wall of the tube I and the anode and cathode, respectively.
  • a resistance II is provided for biassing the cathode of V2.
  • the tubes 3 and 4 with their central conductors constitute the inductances Ls and L7 of Fig. 5.
  • the side tube 3 is omitted, as shown in Fig. 11.
  • the central conductor I of the side tube 4 is connected to the central conductor 2 which in this case has no Ablocking condenser dividing it into two parts.
  • the high tension for the anode of V1 is supplied through the conductors 'I and 2.
  • Both the cathode heater leads I0 and I2 for the valve V2 are passed through the conductor 1, but both ends of the heater are coupled thereto by bypass condensers K.
  • the remaining elements of Fig. 11 which have not been mentioned are the same as in Fig. 10.
  • An electric wave amplifier comprising two thermionic tubes each having a cathode and an anode, a hollow conductor having said tubes mounted therein, a grounded grid in each of said tubes directly connected to said hollow conductor and forming a substantially perforated partition thereacross, two conductors mounted insde said hollow conductor between said tubes and forming a coaxial conductor line with said hollow conductor, a direct current blocking xcondenser connecting said two conductors together, said two conductors being directly connected one to the anode of one of said tubes and the other to the cathode of the other of said tubes, and two f quarter wave coaxial line type stubs connected across said coaxial conductor, one adjacent said one tube and the other adjacent said other tube, said stubs being dimensioned to inductively load said coaxial conductor, said coaxial conductor being dimensioned to couple inductively said tubes together, the input and output inter-electrode capacities of said tubes forming with the coaxial elements a transforming filter adapted
  • An amplifier according to claim 1 in which additional capacities are respectively connected in shunt between the anode and grid of said one tube and between the cathode and grid of each other tube.
  • An electric Wave amplier comprising two thermionic tubes each having a cathode and an anode, a hollow conductor having saidy tubes mounted therein, a grounded grid in each of said tubes directly connected to said hollow conductor and forming a substantially perforated partition thereacross, two conductors mounted inside said hollow conductor between said tubes and forming a coaxial conductor line with said hollow conductor, said two conductors being directly connected onev to the anode of one of said tubes and the other to the cathode of the other of said tubes and a blocking condenser coupling said two conductors together, a coaxial line type stub connected across said coaxial conductor line, said stub being dimensioned to inductively load said coaxial line, said coaxial line being dimensioned to inductively couple said tubes, the input and output inter-electrode capacities of said tubes forming with the coaxial elements a transforming filter adapted to pass a frequency band of given band width.
  • An amplifier according to claim 4 in which the inner conductor of said coaxial line type stub is hollow and insulated from the outer conductor thereof and directly connected to the anode of said one tube for applying an operating potential thereto, and an additional conductor is arranged inside said hollow conductor and directly connected to the anode of said other tube for applying an operating potential thereto.
  • An amplier according to claim 4 further comprising additional capacities connected in shunt between the anode and grid of said one tube and between the cathode and grid of said other tube.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Hybrid Cells (AREA)
  • Electrotherapy Devices (AREA)
  • Networks Using Active Elements (AREA)
US581098A 1943-12-28 1945-03-05 Wide frequency band amplifier Expired - Lifetime US2524821A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB21765/43A GB588292A (en) 1943-12-28 1943-12-28 Improvements relating to wide frequency band radio amplifiers

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US (1) US2524821A (en(2012))
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ES (1) ES178574A1 (en(2012))
FR (1) FR933247A (en(2012))
GB (1) GB588292A (en(2012))

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2673253A (en) * 1948-02-14 1954-03-23 Emi Ltd Thermionic valve amplifier
US2751443A (en) * 1953-09-28 1956-06-19 Bendix Aviat Corp Coaxial low-noise amplifier
US2753525A (en) * 1952-08-20 1956-07-03 Itt Pulsed r. f. amplifier
US2756283A (en) * 1951-11-13 1956-07-24 Rca Corp Cathode input amplifiers
US2759101A (en) * 1953-03-18 1956-08-14 Lab For Electronics Inc High frequency apparatus
US2760060A (en) * 1952-12-11 1956-08-21 Rca Corp Ultra-high frequency converter system having crystal diode mixer
US2775656A (en) * 1950-09-27 1956-12-25 Emi Ltd Electron discharge tube amplifiers
US2775659A (en) * 1951-02-20 1956-12-25 Standard Coil Prod Co Inc Cascode circuits
US2802066A (en) * 1953-07-01 1957-08-06 Rca Corp Wide-band high frequency amplifier
US2803710A (en) * 1953-04-21 1957-08-20 Itt Tuned high frequency amplifier
US2817719A (en) * 1955-12-30 1957-12-24 Collins Radio Co U. h. f. low noise amplifier
US2881265A (en) * 1951-04-04 1959-04-07 Rca Corp Wide-band amplifier circuits for television receivers and the like
US2902546A (en) * 1954-04-22 1959-09-01 Rca Corp Tuned amplifier neutralization system
US2930936A (en) * 1956-08-02 1960-03-29 M aker
DE1105483B (de) * 1952-11-27 1961-04-27 Telefunken Patent Schaltung zur additiven Mischung von elektromagnetischen Schwingungen
US3098208A (en) * 1958-09-29 1963-07-16 Gen Electric Coupling circuit for connecting together two resonant circuits and tuning the whole over a band of frequencies
US3155918A (en) * 1960-12-08 1964-11-03 Gen Electric Coupling grid means for grounded grid amplifier
US3244998A (en) * 1963-07-10 1966-04-05 Collins Radio Co Impedance matched broad band transistor amplifier
US3641452A (en) * 1970-07-02 1972-02-08 Willie L Steed Pi-coupled low-noise amplifier
US3800210A (en) * 1971-03-16 1974-03-26 Jeumont Schneider System for the electric supply of a variable capacitive load

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2747138A (en) * 1952-10-24 1956-05-22 Bell Telephone Labor Inc Broad band amplifier devices

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1896534A (en) * 1927-05-13 1933-02-07 Gen Electric Electrical system
US2107387A (en) * 1934-10-04 1938-02-08 American Telephone & Telegraph Vacuum tube with tank circuits
US2143671A (en) * 1937-06-04 1939-01-10 Rca Corp Ultra short wave circuit
US2149356A (en) * 1936-09-12 1939-03-07 Bell Telephone Labor Inc Wave transmission network
US2284529A (en) * 1939-08-04 1942-05-26 Bell Telephone Labor Inc Wave transmission network
US2321521A (en) * 1941-01-10 1943-06-08 Farnsworth Television & Radio Frequency band filter
US2419800A (en) * 1941-05-10 1947-04-29 Standard Telephones Cables Ltd Ultra high frequency amplifier
US2426185A (en) * 1941-09-27 1947-08-26 Bell Telephone Labor Inc Translation of microwaves

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1896534A (en) * 1927-05-13 1933-02-07 Gen Electric Electrical system
US2107387A (en) * 1934-10-04 1938-02-08 American Telephone & Telegraph Vacuum tube with tank circuits
US2149356A (en) * 1936-09-12 1939-03-07 Bell Telephone Labor Inc Wave transmission network
US2143671A (en) * 1937-06-04 1939-01-10 Rca Corp Ultra short wave circuit
US2284529A (en) * 1939-08-04 1942-05-26 Bell Telephone Labor Inc Wave transmission network
US2321521A (en) * 1941-01-10 1943-06-08 Farnsworth Television & Radio Frequency band filter
US2419800A (en) * 1941-05-10 1947-04-29 Standard Telephones Cables Ltd Ultra high frequency amplifier
US2426185A (en) * 1941-09-27 1947-08-26 Bell Telephone Labor Inc Translation of microwaves

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2673253A (en) * 1948-02-14 1954-03-23 Emi Ltd Thermionic valve amplifier
US2775656A (en) * 1950-09-27 1956-12-25 Emi Ltd Electron discharge tube amplifiers
US2775659A (en) * 1951-02-20 1956-12-25 Standard Coil Prod Co Inc Cascode circuits
US2881265A (en) * 1951-04-04 1959-04-07 Rca Corp Wide-band amplifier circuits for television receivers and the like
US2756283A (en) * 1951-11-13 1956-07-24 Rca Corp Cathode input amplifiers
US2753525A (en) * 1952-08-20 1956-07-03 Itt Pulsed r. f. amplifier
DE1105483B (de) * 1952-11-27 1961-04-27 Telefunken Patent Schaltung zur additiven Mischung von elektromagnetischen Schwingungen
US2760060A (en) * 1952-12-11 1956-08-21 Rca Corp Ultra-high frequency converter system having crystal diode mixer
US2759101A (en) * 1953-03-18 1956-08-14 Lab For Electronics Inc High frequency apparatus
US2803710A (en) * 1953-04-21 1957-08-20 Itt Tuned high frequency amplifier
US2802066A (en) * 1953-07-01 1957-08-06 Rca Corp Wide-band high frequency amplifier
US2751443A (en) * 1953-09-28 1956-06-19 Bendix Aviat Corp Coaxial low-noise amplifier
US2902546A (en) * 1954-04-22 1959-09-01 Rca Corp Tuned amplifier neutralization system
US2817719A (en) * 1955-12-30 1957-12-24 Collins Radio Co U. h. f. low noise amplifier
US2930936A (en) * 1956-08-02 1960-03-29 M aker
US3098208A (en) * 1958-09-29 1963-07-16 Gen Electric Coupling circuit for connecting together two resonant circuits and tuning the whole over a band of frequencies
US3155918A (en) * 1960-12-08 1964-11-03 Gen Electric Coupling grid means for grounded grid amplifier
US3244998A (en) * 1963-07-10 1966-04-05 Collins Radio Co Impedance matched broad band transistor amplifier
US3641452A (en) * 1970-07-02 1972-02-08 Willie L Steed Pi-coupled low-noise amplifier
US3800210A (en) * 1971-03-16 1974-03-26 Jeumont Schneider System for the electric supply of a variable capacitive load

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Publication number Publication date
ES178574A1 (es) 1947-08-16
BE477660A (en(2012))
FR933247A (fr) 1948-04-14
GB588292A (en) 1947-05-20

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