US2383710A - Thermionic valve circuits - Google Patents

Thermionic valve circuits Download PDF

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Publication number
US2383710A
US2383710A US525815A US52581544A US2383710A US 2383710 A US2383710 A US 2383710A US 525815 A US525815 A US 525815A US 52581544 A US52581544 A US 52581544A US 2383710 A US2383710 A US 2383710A
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United States
Prior art keywords
resistance
voltage
anode
thermistor
valve
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Expired - Lifetime
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US525815A
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English (en)
Inventor
Chatterjea Prafulla Kumar
Scully Charles Thomas
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STC PLC
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Standard Telephone and Cables PLC
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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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/34—DC amplifiers in which all stages are DC-coupled
    • H03F3/36—DC amplifiers in which all stages are DC-coupled with tubes only
    • 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

Definitions

  • valve amplifying circuits and employs a non-linear resistance element, preferably a thermistor, t obtain an efiicient intervalve coupling which will transmit direct currents.
  • a non-linear resistance element preferably a thermistor
  • the principal object of this invention is to get over the difficulty by providing a coupling network which transmits direct current and which steps down the mean anode voltage to a much greater degre than the anode voltage variations' due to an applied signal; and the conditions may even be chosen so that it amplifles the voltage variations by stepping them up to the grid while still stepping down the anode voltage.
  • the invention may comprise in a multistage thermionic valve amplifier, a coupling network adapted to transmit direct currents and to transfer the variations of the anode voltage of one valve substantially unaltered to the control grid of the following valve while applying only a fraction of the mean anode voltage thereto, the network comprising a non-linear resistance element combined with one or more resistances.
  • the invention consists in an lntervalve coupling network for a multistage thermionic valve amplifier adapted to transmit direct currents, comprising athermistor having a negative temperature coeiiicient of resistance and one or more resistances so disposed as to transfer amplified anode voltage variations oi one valve to the controlgridy of the next folordinary constant resistance.
  • Fig. 1 shows a schematic circuit diagram oian amplifier according to the invention
  • Figs. 2 and 4 show characteristic curves t0 explain the operation of Fig. 1;
  • Fig. 3 shows a two-stage coupling network according to the invention.
  • the invention employs in the coupling network a non-linear resistance of semi-conducting material, that is, a resistance in which the relation between the current and the corresponding potential difference is not a straight line as in an
  • a non-linear resistance of semi-conducting material that is, a resistance in which the relation between the current and the corresponding potential difference is not a straight line as in an
  • This may be a voltage dependent resistance of a carborundum basis or the like, the properties of which are described for instance in the Post Ofiice Electrical Engineers Journal, January 1942 page 180.
  • the special properties of the temperature dependent resistance elements known as thermistors are employed, since by their use it is possible to obtain amplification in the coupling network.
  • Thermistors have vbeen in use for some years, and are composed of semi-conducting materials characterized by a temperature coefficient of reslstance which may be either positive or negative and which is moreover many times the corresponding coeiiicient for a pure metal such as copper. Ihis property renders thermistors particularly suitable for a variety of special applications in electric circuits.
  • a resistance material havingV a high negative temperature coeilicient of resistance comprises a mixture of manganese oxide and nickel oxide, with orwithout the addition of certain other metallic oxides, the mixture being suitably heat treated.
  • Thermistors have been employed in two different forms (a) known as a directly heated thermistor and comprising a resistance element of the thermally sensitive resistance material provided with suitable lead-out conductors or terminals, and (b) known as an indirectly heated thermistor comprising the element (a) provided in addition with a heating coil electrically insulated from the element.
  • a directly heated thermistor is primarily intended to be controlled by the current which flows through it and which varies the temperature and also the resistance accordingly. Such a. thermistor will also be affected by the temperature oi its surroundings and may therefore be used for thermostatic control and like purposes with or without direct heating by the current flowing through it.
  • An indirectly heated thermistor is chiefly designed to be heated by a controlling current which flows through the heating coll and which will usually, but not necessarily, be different from the current which flows through the resistance element. but this type of thermistor may also be subjected to either or both of the types of control applicable to e. directly heated thermistor.
  • Fig. 1 shows a simple two-valve amplifier ernploying an intervalve coupling network according to the invention.
  • the two valves Vi and V2 are supplied with anode voltage from the hightension source connected to the terminal -l-HT through appropriate resistances A.
  • the anode of V1 is connected to the control grid of V2 through a coupling network containing in series a directly heated thermistor T having a resistance element R, together with a resistance R1, and in shunt a resistance R2 connected to the control grid of V2 in series with a small biassing battery B.
  • a signal voltage e is applied to the control grid of V1 at the input terminals i, 2, and the output is taken from the anode of V: through terminals 3, 4 by any appropriate means (not shown). It will be understood that there may be other valve stages before or after Vi and V2 adapted to translate the signal in any way.
  • the curve designated R in Fig. 2 is a typical curve showing the relation between the voltage and the current for a thermistor, which is assumed to have a negative temperature coenicient of resistance. This curve has an initial portion with a positive slope for currents up to about 1.2 corresponding to a voltage of 6.9; and afterwards the slope is negative, giving an unstable condition. If a voltage greater than 6.9 ls applied to the thermistor, the current will increase spontaneously until the thermistor is destroyed or until some other factor operates to limit the current.
  • R1 and Ra respectively show the characteristic for the resistances R1 and Rz above. They have a constant positive slope.
  • the curve R+R1 is obtained and represents the voltage across R and R1 together.
  • the curve R+R1+R2 represents the voltage v (Fig. l) across the whole combination.
  • the coupling network accordlng to the invention steps down the mean anode voltage without stepping down its variations.
  • the mean voltage represented by 1.9 is too large to apply to the control grid, it may be offset by the battery B shown in Fig. l, or by any other convenient biassing arrangement of ordinary type.
  • the potential difference v is proportional to the signal voltage e.
  • the operating conditions should be chosen according to the manner of variation of the signal: Thus, if the signal varies on either side of a mean value which represents the no signal condition, the resistances R. Ri and R: should be chosen so that the corresponding mean value of v (namely 7.9 in the case of Fig. 2) should produce the current corresponding to the mean of the ordinates C1 and Cz on the curve R+R1+Rz (about 5.55). If, however, the variation is all one way, then the resi condition should correspond to one of the ordinates C1 or C2.
  • the mean voltage applied to the control grid of Vn may be reduced without reducing the permissible range of variation of v.
  • the coupling network may be caused to introduce a voltage amplification.
  • the nat part of the curve R+R1 moves to the right, bringing a portion with a negative slope between the ordinates Ci and Cz.
  • the slope of the line Ra will now be greater than the slope of that part of the curve R+Ri+Rz which lieslbetween the ordinates Ci and Cz.
  • the variation of voltage across R is now greater than the variation of v.
  • the curve R may be altered by passing a suitable current through the heating coil.
  • the eiIect is mainly to reduce all the ordinates of the curve R, producing a flatter curve Rn, Fig. 2, with a less sharp maximum.
  • the ordinates for large values of current through the element are less.
  • the operating point may be very easily adjusted-as required. If, for example. the variations of v are small compared with the range defined by the ordinates Ci and Cz, the operating point may be shifted about within this range in order to 11nd the most favourable position.
  • Fig. 3 shows another network Ta, Ra, R4 and Re connected infront oi the loriginal coupling network' between the anode of Vr and the control grid oi' Va. From what has been said, it will be clear that the mean anode voltage can be stepped down twice, while the variations are substantially unaltered, or may b e ampliiied in each stage. In choosing the values of the second network, account must be taken of the shunting eilect oi' the nrst network on Rs. which must be increased accordingly.
  • the mean anode voltage may clearly be stepped down in more than two stages if desired, by providing the network with any desired number vof additional meshes of the same kind.
  • Any of the thermistors may be of the indirectly heated type, to allow for adjustments of the characteristic as already explained.
  • Fig. 4 shows the characteristic curve (Z) ⁇ of the voltage dependent resistance to arbitrary scales.
  • the line Rz is for the resistance R2 as in Fig. 2, and the curve Z+R2 is for the two together obtained by adding the ordinates of the Z and Ra curves.
  • the corresponding anode voltage variation is from about 4.5 5.8, that is, a total variation of 1.3, the mean voltage beingabout 5.15.
  • the corresponding variation of voltage across R2 is from 0.9 to 1.5, a total of 0.6, the mean voltage being 1.2.
  • the voltagevariation applied to the control grid is a little less than half the anode voltage variation, but the mean voltage applied has been stepped down to less than a quarter.
  • the counteracting bias for the valve V2 may be provided without the use of the battery B, if preferred.
  • the resistance Rz is connected directly to earth.
  • the two cathodes are then connected together and to earth through the resistance element of an additional thermistor (not shown), having a negative temperature coeiiicient of resistance.
  • This thermistor should preferably be of the indirectly heated type, and an appropriate current should be passed through the heating coil from a local circuit to produce a characteristic curve like Rn (Fig. 2), having a fairly fiat maximum at M.
  • the thermistor should be selected so that the combined cathode currents which flow through it correspond to the abscissa of the point M, and the corresponding ordinate should at the same time correspond to the desired counteracting voltage. By this means the value of this voltage will be substantially independent of the variations inthe cathode currents caused by the signal, and the necessity for the battery B is avoided.
  • This arrangement may be adopted when the coupling network has any number of meshes.
  • the characteristic feature of this invention is a coupling network which transmits direct current, but which applies to the control grid a proportion of the anode voltage variation larger than the proportion of the mean anode voltage so applied.
  • proportion is to be understood to include proportion values greater than l.
  • means for coupling the anode of onevalve to the control grid of the following valve said means including a. network adapted to transmit direct current and comprising a non-linear resistance element and at least one ordinary resistance s0 selected and disposed that the proportion of the anode voltage variation transferred. to the grid is greater than the proportion of the mean anode voltage so transferred.
  • means for coupling the anode of one valve to the control grid of the following valve including a coupling network comprising a nonlinear resistance element and at least one ordi nary resistance adapted to transmit direct currents and to transfer the variations of the anode voltage of one valve substantially unaltered to the control grid of the following valve while applying only a fraction of the vmean anode voltage thereto.
  • the network comprises a thermistor having a negative temperature coefiicient of resistance and at least one ordinary resistance so disposed as to transfer 'amplified anode voltage variations of one valve to the control grid of the next following valve, while applying a fraction of the mean anode voltage to the said grid.
  • non-linear resistance element is a voltage dependent resistance of the carborundum type, and connected in series between the anode and the control grid, while at least one of the ordinary resistances is connected in shunt between the control grid and cathoderof the following valve.
  • the network comprises a thermistor having a negative temperature coefficient of resistance connected in series with a first ordinary resistance between the anode and thecontrol grid, and a second ordinary resistance -connected in shunt between the controlgrid and cathode of the'following valve.
  • means for coupling the anode of one valve to the control grid ofthe following valve including a network adapted to transmit direct current and comprising a non-linear resistance element and at least one ordinary resistance so selected and disposed that the proportion of the anode voltage variation transferred to the grid is greater than the proportion of the mean anode voltage so transferred, a non-linear resistance element comprising a thermistor having a negative temperature coetilcient of resistance, the resistance element of the thermistor being connected in series with a rst resistance between the anode and the control grid, a second resistance being connected in shunt between the control grid and cathode of the following valve.
  • a multi-stage thermionic valve amplifier means for coupling the anode of one valve to the control grid of the following valve, said means including a coupling network adapted to transmit direct current and to transfer the variations of the anode voltage of one valve substantially unaltered to the control grid of the following valve while applying only a fraction of the mean anode voltage thereto, said network comprising a nonlinear resistance including a thermistor and at least one ordinary resistance, the operating point of the thermistor being set between ordinates which bound a substantially flat portion of the characteristic curve of the voltage dependent on the surn of said resistances.
  • the network comprises a thermistor having a resistance with a negative temperature coefficient of resistance, connected in series with a rst ordinary resistance between said anode and said control grid, and a second ordinary resistance connected in shunt between the control grid and cathode of said following valve, the operating point of the thermistor being set between ordinates which bound a substantially nat portion of the charac* teristic curve of the voltage dependent on the sum of said three resistances.
  • An amplifier according to claim 13 in which the network comprises a thermistor having a resistance with a negative temperature coemcient oi' resistance connected in series with a first ordinary resistance between said anode and said control grid, and a second ordinary resistance connected in shunt between the control grid and cathode of said following valves, the operating point of the thermistor being set on an ordinate of the characteristic of the voltage dependences which cuts the characteristic curve of the voltage dependent on the sum of the two first-mentioned resistances at a point of negative slope and cuts the characteristic curve of the voltage dependent on the sum of all three resistances at a point of positive slope.
  • a second network connected in front ot the original coupling network between said anode and said control grid. comprising at least one thermistor of the indirectly heated type.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Thermally Actuated Switches (AREA)
  • Thermistors And Varistors (AREA)
US525815A 1943-05-14 1944-03-10 Thermionic valve circuits Expired - Lifetime US2383710A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB256970X 1943-05-14

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US2383710A true US2383710A (en) 1945-08-28

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US525815A Expired - Lifetime US2383710A (en) 1943-05-14 1944-03-10 Thermionic valve circuits

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US (1) US2383710A (sl)
BE (1) BE469233A (sl)
CH (1) CH256970A (sl)
FR (1) FR928874A (sl)
GB (1) GB565609A (sl)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2524953A (en) * 1947-07-05 1950-10-10 Automatic Telephone & Elect Electronic trigger circuits
US2554905A (en) * 1946-06-01 1951-05-29 Seismograph Service Corp Seismic signal amplifier
US2794864A (en) * 1952-08-01 1957-06-04 Bell Telephone Labor Inc Nonreciprocal circuits employing negative resistance elements
US2885612A (en) * 1957-01-02 1959-05-05 Honeywell Regulator Co Symmetrically operating servosystem with unsymmetrical servoamplifier
US3088325A (en) * 1959-05-25 1963-05-07 Westinghouse Air Brake Co Snap-acting safety valve device

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB751533A (en) * 1953-04-28 1956-06-27 Philips Electrical Ind Ltd Improvements in or relating to direct voltage amplifier circuits

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2554905A (en) * 1946-06-01 1951-05-29 Seismograph Service Corp Seismic signal amplifier
US2524953A (en) * 1947-07-05 1950-10-10 Automatic Telephone & Elect Electronic trigger circuits
US2794864A (en) * 1952-08-01 1957-06-04 Bell Telephone Labor Inc Nonreciprocal circuits employing negative resistance elements
US2885612A (en) * 1957-01-02 1959-05-05 Honeywell Regulator Co Symmetrically operating servosystem with unsymmetrical servoamplifier
US3088325A (en) * 1959-05-25 1963-05-07 Westinghouse Air Brake Co Snap-acting safety valve device

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Publication number Publication date
BE469233A (sl)
FR928874A (fr) 1947-12-10
GB565609A (en) 1944-11-17
CH256970A (de) 1948-09-15

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