US2093094A - Radio frequency amplifier - Google Patents

Radio frequency amplifier Download PDF

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Publication number
US2093094A
US2093094A US640384A US64038432A US2093094A US 2093094 A US2093094 A US 2093094A US 640384 A US640384 A US 640384A US 64038432 A US64038432 A US 64038432A US 2093094 A US2093094 A US 2093094A
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United States
Prior art keywords
grid
screen
grids
condenser
frequency
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Expired - Lifetime
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US640384A
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English (en)
Inventor
Harold O Peterson
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RCA Corp
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RCA Corp
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Priority to NL37458D priority Critical patent/NL37458C/xx
Priority to DEP49612D priority patent/DE447309C/de
Application filed by RCA Corp filed Critical RCA Corp
Priority to US640384A priority patent/US2093094A/en
Priority to FR762941D priority patent/FR762941A/fr
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Publication of US2093094A publication Critical patent/US2093094A/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

Definitions

  • Y RADIO FREQUENCY AMPLIFIER Filed oct. ⁇ 31, 1932 2 sheets-sheet 1 INVENTOR- HAROLD O.
  • PETERSON ATTORNEY- Sept. 14, 1937'. o.4 PETERSON RADIO FREQUENCY AMPL IFIER Filed 001'.. 51, 1932 2 Sheets-Sheet 2 INVENTOR- HAROLD o.
  • This invention relates to improvements in amplifier circuits, and more particularly to tube amplifiers which are operated at high radio frequencies.
  • Vacuum' tubes of the screen grid type have for a number of years been used quite effectively for the amplification of very high radio frequencies. I have noted however, that such radio frequency amplifiers do not always operate with perfect stability at some of the high frequencies for which they have been designed. Since such amplifier units are generally very well shielded and all supply leads effectively filtered, it is believed that the instability observed is due to residual capacity coupling from plate to grid. The effective value of plate to grid capacity coupling becomes more and more effective as a means for producing regenerative oscillations as frequency is increasing, for the reason that the reactance of a given amount of capacity coupling decreases with increase of frequency. There is also another effect which tends to increase the effective value' of plate to grid capacity in screen grid tubes.
  • this undesirable tendency to oscillate is eliminated by connecting the screen grid to ground through a condenser of such value as to resonate with the inductance of the screen grid lead at the frequency on which the tendency to oscillate is experienced.
  • This series resonance eil'ect will re- Iduce the tendency to oscillate over a band of frequencies centering about the frequency to which the screen by-passing circuit is tuned.
  • Fig. 1 is a wiring diagram of a conventional short wave radio frequency receiver amplifier employing screen grid tubes;
  • Fig. 2 is a diagram of a grid grounding circuit
  • Fig. 3 is a curve showing a desirable over-all characteristic which may be obtained by the use of my invention.
  • Fig. 4 is a wiring diagram of a push-pull radio frequency amplifier utilizing the features of my invention
  • Fig. 5 is a wiring diagram of another modification of a push-pull radio frequency amplifier utilizing the features of my invention.
  • Fig. 6 is a wiring diagram of an oscillator utilizing the features of my invention.
  • the antenna I energizes the input circuit 5, 6 through inductance 2 grounded at 3.
  • a suitable shield 4 is interposed between the antenna primary inductance 2 and the secondary inductance 5.
  • the input circuit is tuned by a variable condenser 6.
  • the vacuum tube 1 of the first radio frequency stage is of the Pentode type having in addition to the customary control grid 8 a screen grid 9 which normally prevents feed back and, consequently, undesired parasitic oscillation generation.
  • a suppressor grid I0 suppresses the secondary emission from the plate.
  • the cathode II is by-passed to ground by a condenser I2 and is also provided with a radio frequency choke I3.
  • the screen grid 9 is by-passed to ground by a condenser I4.
  • the suppressor grid I0 is bypassed to ground by a condenser I5 and resistance I6 connected in parallel.
  • a proper predetermined selection of the correct values of capacity is necessary for the by-pass condensers I2, I4 and I5, as will be explained in further detail later.
  • receiver circuit Other parts of the receiver circuit are the RF transformer I1, tuning condenser I8, second radio frequency amplifier tube I9, radio frequency transformer 20, tuning condenser 2I, detector tube 22, audio frequency transformer 23 and audio tube 24, which are connected to phones 25.
  • the screen grid lead of length L has an appreciable inductance at very high frequencies. This effective inductance is indicated by the dotted inductance coil.
  • condenser I4 is of such a capacity value as to resonate with the inductance of lead L at a wave length of I4 meters or a frequency of 21,430 kilocycles.
  • condenser I5 is chosen so as to series resonate with its grid lead at I5 meters or a frequency of 20,000 kilocycles.
  • Condenser I4a is chosen in value to series resonate with its grid lead at I6 meters or 18,750 kilocycles.
  • Condenser I5a tunes its grid lead to 17 meters, or 17,640 kilocycles.
  • the other grid condensers are chosen to resonate at different frequencies at which parasitics tend to occur. For the entire receiver a form of band stabilizing characteristic such as shown by the curve in Fig. u
  • each of the condensers I4a, I5a, I4 and I5 cause grid lead tunings such as indicated by the overlapping curves A, B, C and D.
  • each characteristic curve overlap as one may tune all grid grounding circuits alike and get a suitable width or band pass by a suitable choice of constants, as, for example, by paralleling each condenser with a resistance.
  • resistances I6 and IBa have been placed in parallel with the suppressor grid series tuning condensers.
  • lumped inductances may be used.
  • Fig. 4 shows a push-pull radio frequency amplier stage having a primary input coil 30, electrostatic shield 3
  • the tubes 31 and 38 have control grids 39 and 40 connected in phase opposition to the secondary coil 32.
  • the suppressor screen 4I and 42 of both tubes are connected to ground through a tuning condenser 43 paralleled by resistance 44.
  • the screen grids of both tubes are connected to ground by a tuning condenser 45.
  • the i plate of tubes 31 and 38 are connected to the primary coil 46 of the next stage which is also tuned by a pair of variable condensers 41 and 48.
  • the tubes also have cathodes 49 and 50 grounded as indicated.
  • a shield 54 is interposed between the primary coil 46 and secondary coil 55.
  • the condenser 43 tunes the suppressor grid structure to series resonate at a frequency about which stabilization is desired. Similarly, condenser 45 tunes the screen grid leads to the same or to another frequency.
  • the modification shown in Fig. 5 is also a push-pull radio frequency amplifier stage, but differs from that of Fig. 4 in that each screen grid and suppressor grid has an individual grid ,f
  • lead tuning condenser which are adjusted to the same, widely different, or adjacent or overlapping frequency bands at which parasitics tend to occur.
  • the circuit comprises priand 61 with heated cathodes 88 and 68.
  • Tubes 84 and 65 also have control grids 10 and 1
  • are of predetermined capacity in order to tune to series resonance the respective grid leads.
  • the use of separate condensers presents the advantage of individual adjustment of each tube.
  • the resistances 82 and 83 of Fig. 5 maintain the suppressor grids at a suitable unidirectional potential in respect to the cathode, as well as broadening the series tuned circuit formed of grid lead and condenser.
  • Other parts of the circuit are the tuning condenser 84, primary coil 85, shield 88 and secondary output coil 8l.
  • Fig. 1 shows a complete circuit of a conventional radio frequency amplifier
  • other forms of circuits may be employed with the grids of their respective stages tuned to the operating or parasitic range of frequencies as described above.
  • the circuits may be located in shielded compartments and the power supply leads thoroughly filtered against potential variations.
  • the individual by-pass condensers of the push-pull arrangements may be selected purposely to tune each grid lead to the different b'and pass frequencies so asto accomplish the overlapping effect as shown by the curve in Fig. 3.
  • my present invention may be applied to frequency multiplier stages of a transmitting system in which case Figures 4 and 5 by .suitable choice of grid bias applied through the minus C lead and by suitable tuning of the output circuits to harmonic frequencies may be made to act as frequency multipliers. More specifically, by impressing a. high negative bias upon the grids 39, of Figure 4 through the minus C lead and coil 32 such that only positive peaks of applied input potential from primary coil 30 cause plate current to flow, then odd harmonics may be obtained in the output circuit consisting of coils 46 and condensers 41 and 40 by suitably tuning them to the harmonic frequency. For even harmonics the plates of tubes 31, 38 would be connected in parallel and then feed in such parallel relation to a suitable parallel tuned circuit having a. variable condenser and inductance coil connected in parallel.
  • the screen grids would be grounded as illustrated through condenser of such a value as to tune the screen grid inductance structure so as to series resonate at some parasitic frequency.
  • the condenser 45 may, of course, be paralleled with a suitable resistance, and the parallel combination may be further paralleled by a suitable inductance coil or connected in series with an inductance coil to give the desired operating characteristic.
  • each grid lead that is to say, the grid leads to the suppressor grids and. screen grids, to a different band of frequencies as indicated by curves a, b, c, and d of Figure 3, an over-all characteristic for the push-pull arrangement shown in Figure 5 will be obtained as shown by the dotted lines in Figure 3.
  • 'I'his dotted line indicates the range over which effectively no regenerative action will take place and secondly indicates the range over which exceedingly stable operation occurs.
  • the mean frequency transmitted by the push-pull system of tubes shown in Figure 5 lies intermediate curves b and c of Figure 3, although it is to be clearly understood that the various condensers may beso chosen so that all of the curves of Figure 3 coalesce into a single curve. Or, the various condensers may be so chosen, together, with, of course, resistances and lumped inductors to produce efcient grounded grids at various Widely separated frequencies or bands of frequencies.
  • each grid lead structure may be connected in parallel to ground through several condensers, each of which tunes the same grid to a different frequency. In this manner, due to series resonance at these different frequencies, the various grids may be maintained at ground potential over a band of frequencies or at particular separated isolated frequencies.
  • my present invention may be applied to oscillators, for example, to prevent feed-back through the tube system, screen and/or suppressor grids may be used, grounded in accordance with my present invention. Controllable feedback may then be had by the use of variable tickler coils or by means ofl variable condensers.
  • FIG. 6 typical inductive feed-back circuit is shown in Figure 6.
  • the screen grid tube 90 is provided witha screen grid
  • the screen grid lead has an inductance of approximately 0.1 michrohenry at a parasitic feed-back frequency of 20,000
  • a high frequency circuit comprising an electron discharge device having within an hermetically sealed container an anode, a. cathode, a control grid adjacent said cathode, a second grid adjacent said control grid, a third grid intermediate said second grid and said anode, said second and third grids having leads having appreciable inductive reactance of approximately 0.1 microhenry at the operating frequency of 20,000 kilocycles, and predetermined values of capacitive circuits in the order of 635 micro-microfarads connecting said leads to ground for maintaining said second and third grids through series resonance effects at ground potential for said operating frequencies.
  • a high frequency circuit comprising an electron discharge device having within an hermetically sealed container an anode, a cathode, a control grid adjacent said cathode, and another electrode intermediate said control electrode and cathode, said other electrode having a lead having appreciable inductive reactance of approximately 0.1 microhenry at a parasitic frequency of 20,000 kilocycles, and a condenser having a predetermined value of capacity inthe order of 635 micro-microfarads shunted by a resistance for connecting said lead to ground for maintaining said other electrode through series resonance effects at ground potential.
  • a high frequency circuit comprising an electron discharge device having Within an hermetically sealed container an anode, a cathode, a control grid adjacent said cathode, a second grid adjacent said control grid, a third grid intermediate said second grid and said anode, said second and third grids having leads having appreciable inductive reactance of approximately 0.1 microhenry at parasitic frequencies of 20,000 kilocycles, and a condenser having a predetermined value of capacity of the order of 635 microfarads shunted by a resistance for connecting each of said leads to ground for maintaining said second and third grids through series resonance effects at ground potential.
  • a high frequency circuit comprising a pair of electron 4discharge devices, each having within an hermetically sealed container an anode, a cathode, a control grid adjacent each cathode, and a screen grid intermediate said control grid and anode, a lead for said screen grid having appreciable inductance through a range of operating frequencies of said device, means for connecting said control grids in phase opposition, a high frequency circuit connected to said anodes, and a condenser connected to each of said screen grids and ground, said condensers being of such a value as to series resonate with the inductance of the screen grid leads whereby said screengrids are maintained at ground radio frequency potential at certain parasitic frequencies.
  • a high frequency circuit comprising a pair of electron discharge devices each having within ⁇ an hermetically sealed container an anode, a cathode, a control grid adjacent each cathode and a screen grid intermediate said control grid and anode, a lead for said screen grid having appreciable inductance through a range of operating frequencies of said device, a suppressor grid intermediate said screen grid and said anode, means for connecting said control grids in phase opposition, a high frequency circuit connected to said anodes, and a condenser connected to each of said screen grids and ground, said condenser being of such a value as to series resonate with the inductance of the screen grid leads whereby said screen grids are maintained at ground radio frequency potential at certain parasitic frequencies.
  • a high frequency circuit comprising a pair of electron discharge devices each having within an hermetically sealed container an anode, a cathode, a control grid adjacent each cathode and a screen grid intermediate said control grid and anode, a lead for said screen grid having appreciable inductance through a range of operating frequencies of said device, means for connecting said control grids in phase opposition, a high frequency circuit connected to said anodes, and a condenser connected to each of said screen grids and ground, resistances shunting said condensers, said condensers and said resistances being of such a value as to series resonate with the inductance of the screen grid leads whereby said screen grids are maintained at ground radio frequency potential at certain parasitic frequencies.
  • High frequency apparatus comprising a plurality of high frequency stages each including an electron discharge device having within an evacuated container an anode, a cathode, a control grid, and a screen grid, each of said screen grids having a lead having appreciable inductive reactance at a frequency for which it is undesired that regeneration take place, and, a condenser connected in series with each of said screen grid leads each of said condensers being of such a value as to series resonate with each screen grid lead at said frequencies whereby said screen grids are maintained effectively at ground radio frequency potential thereby preventing the undesired regenerative action.
  • High frequency apparatus comprising a plurality of high frequency stages each including an electron discharge device having within an evacuated container an anode, a cathode, a control grid and a screen grid, each of said screen grids having a lead having appreciable inductive reactance at a frequency for which it is undesired that regeneration take place, and, a condenser connected in series with each of said screen grid leads each of said condensers being of such a value as to series resonate with the screen grid leads of each of said stages to different frequencies whereby said screen grids are maintained effectively at ground radio frequency potential thereby preventing the undesired regenerative action over a band of frequencies.
  • High frequency apparatus comprising 4 ⁇ a plurality of high frequency stages each including an electron discharge device having within an evacuated container an anode, a cathode, a control grid and a screen grid, each of said screen grids having a lead having appreciable inductive reactance at a frequency for which it is undesired that regeneration take place, and, a condenser connected in series with each of said screen grid leads, a resistance shunting said condensers, each of said condensers and said resistances being of such a value as to series resonate with the screen grid leads of each of said frequency stages to different frequencies whereby said screen grids are ⁇ maintained effectively at ground radio frequency potential thereby preventing the undesired regenerative action.
  • High frequency apparatus comprising a plurality of high frequency stages each including an electron discharge device having Within an evacuated container an anode, a cathode, a control grid and a screen grid, each of said screen grids having a lead having appreciable inductive reactance at a frequency for which it is undesired that regeneration take place, and, a condenser connected in series with each of said screen grid leads, a resistance shunting said condensers, each of said condensers and said resistances being of such a value as to series resonate at different overlapping frequency bands with the screen grid leads of each of said stages to different frequencies whereby said screen grids are maintained effectively at ground radio frequency potential thereby preventing the undesired regenerative action.
  • High frequency apparatus comprising a plurality of high frequency stages each including an electron discharge device having Within an evacuated container an anode, a cathode, a control grid and a screen grid, each of said screen grids having a lead having appreciable inductive reactance at a frequency for which it is undesired that regeneration take place, and, a condenser connected in series with each of said screen grid leads, a lumped inductance shunting said condensers each of said condensers and said lumped inductance being of such a value as to series resonate at different overlapping frequency bands with the screen grid leads of each of said frequency stages to different frequencies whereby said screen grids are maintained effectively at ground radio frequency potential thereby preventing the undesired regenerative action.
  • a high frequency circuit comprising a pair of electron discharge devices each having within an hermetically sealed container an anode, a cathode, a control grid adjacent each cathode and a screen grid intermediate said control grid and anode, a lead for said grid having appreciable inductance through a range of operating frequencies of said device, a suppressor grid intermediate said screen grid and said anode, means for connecting said control grids and said suppressor grids in phase opposition respectively, a high frequency circuit connected to said anodes and a condenser connected to said suppressor grids to tune the grids of different stages to different frequencies whereby said suppressor grids are maintained at ground radio frequency potential at certain parasitic frequencies.
  • a high frequency circuit comprising a pair of electron discharge devices each having within an hermetically sealed container an anode, a cathode, a control grid adjacent each cathode and a screen grid intermediate said control grid and anode, a lead for said grid having appreciable inductance through a range of operating frequencies of said device, a suppressor grid intermediate said screen grid and said anode, means for connecting said control grids and said suppressor grids in phase opposition respectively, a high frequency circuit connected to said anodes, a condenser and a resistance shunting said condenser connected to said suppressor grids, each of said condensers and said resistances being of such a value as to series resonate with the suppressor grid leads whereby said suppressor grids are maintained at ground radio frequency potential at certain parasitic frequencies.
  • a high frequency circuit comprising a pair of electron discharge devices each having within an hermetically sealed container an anode, a cathode, a control grid adjacent each cathode and a screen grid intermediate said control grid and anode, a lead for said grid having appreciable inductance through a range of operating frequencies of said device, a suppressor grid intermediate said screen grid and said anode, means for connecting said control grids and said suppressor grids in phase opposition respectively, a
  • a highfrequency circuit comprising a pair of electron dischargedevices each having within an hermetically sealed container an anode, a cathode, a control grid adjacent each cathode and a screen grid intermediate said control grid and anode, a lead for said grid having appreciable inductance through-a range of operating frequencies of said device, a suppressor grid intermediate said screen grid and said anode, means for connecting said control grids and said suppressor grids in phase opposition respectively, a high frequency circuit connected to said anodes, a condenser and a lumped inductance shunting said condenser connected to said suppressor grids, each of said condensers and said lumped inductance being of such a value as to series resonate at different overlapping frequency bands with the suppressor grid leads whereby said suppressor grids are maintained at ground radio frequency potential at certain parasitic frequencies.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microwave Amplifiers (AREA)
US640384A 1925-01-28 1932-10-31 Radio frequency amplifier Expired - Lifetime US2093094A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL37458D NL37458C (xx) 1932-10-31
DEP49612D DE447309C (de) 1925-01-28 1925-01-28 Regelwiderstand mit einer Spule hohen und einer niedrigen Widerstands
US640384A US2093094A (en) 1932-10-31 1932-10-31 Radio frequency amplifier
FR762941D FR762941A (fr) 1932-10-31 1933-10-26 Amplificateurs de radio-fréquence

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US640384A US2093094A (en) 1932-10-31 1932-10-31 Radio frequency amplifier

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FR (1) FR762941A (xx)
NL (1) NL37458C (xx)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2603723A (en) * 1947-06-03 1952-07-15 Philco Corp High-frequency amplifier circuit
US2691078A (en) * 1951-05-17 1954-10-05 Rca Corp Neutralizing circuits for highfrequency amplifiers
US2790036A (en) * 1955-06-07 1957-04-23 Ben H Tongue Electron-tube stabilized amplifying circuit

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2603723A (en) * 1947-06-03 1952-07-15 Philco Corp High-frequency amplifier circuit
US2691078A (en) * 1951-05-17 1954-10-05 Rca Corp Neutralizing circuits for highfrequency amplifiers
US2790036A (en) * 1955-06-07 1957-04-23 Ben H Tongue Electron-tube stabilized amplifying circuit

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Publication number Publication date
NL37458C (xx)
FR762941A (fr) 1934-04-20

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