US2227026A - Amplifier arrangement for television purposes - Google Patents

Amplifier arrangement for television purposes Download PDF

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Publication number
US2227026A
US2227026A US179566A US17956637A US2227026A US 2227026 A US2227026 A US 2227026A US 179566 A US179566 A US 179566A US 17956637 A US17956637 A US 17956637A US 2227026 A US2227026 A US 2227026A
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Prior art keywords
tube
grid
potential
anode
output
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Expired - Lifetime
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US179566A
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English (en)
Inventor
Schlesinger Kurt
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LOEWE RADIO Inc
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LOEWE RADIO Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/14—Picture signal circuitry for video frequency region
    • H04N5/16—Circuitry for reinsertion of DC and slowly varying components of signal; Circuitry for preservation of black or white level

Definitions

  • the present invention relates to an improvement in television amplifier circuit arrangements.
  • FIG. 1 shows a television amplifier circuit as it is well known
  • Fig. 2 shows a circuit arrangement in accordance with the invention
  • Fig. 2a indicates a change of the circuit system of Fig. 2
  • Fig. 2a indicates a change of the circuit system of Fig. 2
  • Fig. 3 shows a further embodiment of the invention.
  • Fig. 1 A fundamental and most simple circuit arrangement for making this peak potential measurement capable ofi utilisation for the present purpose, as it is already known, is shown in Fig. 1 wherein I is the output stage of the amplifier, the grid of which is coupled byway of a condenser 2 with the preliminary amplifier and is biased by way of a leak resistance 3 from a source 5. If the Br-aun tube is directlyconnected to the tube I or if a positive television transmitter system is used, black is produced when the anode of the tube I has reached its maximum negative value, i. e., when the grid of the end tube has reached its maximum positive value. In accordance with the above the grid oscillations pendul-ating about the bias 5 as mean. value must be prevented from being ever capable of attaining a higher positive momentary value than the stationary value, 1. e., the potential 5 itself. For
  • a two-electrode tube 6 is connected in parallel to the leak resistance 3 having its anode connected to the: grid.
  • the tube 6 in the case of positive oscillations attracts electronic current to its anode for such time until the grid has been negatively charged to the potential of the cathode of tube 6, i. e. to the bias 5. If the grid alternating potential oscillates into negative, the tube 5 remains without current.
  • the circuit arrangement of Fig. 1 nearly realizes that which is required, viz., that the grid alternating potential is never capable of oscillating beyond the value 5 as highest positive peak value, so that the anode alternating potential is also incapable of oscillating below the stationary value of the unexcited condition, i. e. black.
  • Fig. 2 represents a great advantage as compared with Fig. 1 insofar as it is possible by means of a potentiometer I to adjust this slip exactly to zero, and even to over-compensate the same.
  • a potentiometer I As compared with circuits otherwise known for maintaining constant value it has the advantage of simplicity, as no special auxiliary batteries of any kind, stabilizers or the like are required.
  • Fig. 2 there is shown for the sake of better comprehension a. preliminary tube 8, which is coupled by way of the coupling condenser 2 with the output tube I.
  • the leak resistance 3 is connected with the grid bias 5. At the anode resistance 4 there occurs an amplified image signal potential.
  • the two-electrode tube 6 is in this, case excited from the anode circuit of tube I.
  • An excess of alternating potential which is there available, is coupled by way of the coupling condenser 9 with the potentiometer I, and can be connected from there, by a tapping, with the cathode of the two-electrode-ftube 6.
  • the anode of the tube Ii can be applied directly to the grid of the output tube I.
  • the potentiometer 1 is so adjusted that a weakening of the oscillations is effected nearly to an amount of UV.
  • the potential i. e. the reverse curve of the grid alternating potential. If the cathode of the rectifier 6 is excited by this potential, it passes electrons to the anode for such time until anode and cathode have the same negative maximum potential.
  • the condenser 2 is discharged, i. e. the grid of the tube I is discharged slowly by way of the leak resistance 3 back to the normal grid bias 5. From the point of view of bias the grid of the tube, therefore, by reason of the circuit arrangement according to the invention (Fig.
  • the coupling elements 9 and I should preferably allow the passage of all frequencies of the television band which are transmitted by the remaining amplifiers, and that this circuit including condenser 9 and resistance portion 1, therefore, may have the time constant of the coupling condenser 2 and leak resistance 3. If ,the time constant is made smaller, the D. C. addition can be effected only with comparatively brief impulses, so that useful discharge time is lost. Losses in the rectification by loading and starting current are readily compensated by adjustment of the tapping at resistance 1 for somewhat more powerful exciting potentials. The rate of discharge is regulated solely by the circuit including coupling condenser 2 and resistance 3, which for reasons of general image trans- 50 mission conditions must have at least the time constant of an image composition, and preferably a multiple thereof.
  • Suitable sizes for the components are:
  • Fig. 20. indicates the circuit connection of the rectifier 6 for this case. Then the cathode of the tube 6 is connected to the grid of the tube I and its anode is connected to the tap of resistance I.
  • each stage of the amplifier may be regulated per se to absolute values by the method according to the invention (assuming sufiicient alternating potentials are available), if importance is attached to correct D. C. reproduction of the image in this stage, without it being necessary to join up the after-connected stages, for example by D. C. coupling, with a regulated stage.
  • the method according to the invention can be employed with advantage not only in transmission amplifiers but also in the end stage of the televsion receiver.
  • Fig. 3 shows a corresponding connection system.
  • the great difficulty in the output receiving stage consisted up to now in the fact that it was necessary to couple the amplifying tube [0 for the image contents frequencies g-alvanically with the rectifier ll rectifying the carrier frequency. So long as the rectifier II is merely a two-electrode rectifier this method is still capable of being performed. If, however, there is employed a three-electrode tube II, which requires a special plate potential, there occur in the case of D. C.
  • the D. C. coupling between detector II and output stage It] can be omitted entirely.
  • a condenser coupling by way of the coupling condenser 2 and the output stage [0 is regulated per se on a constant basis by the method according to the invention coupling by way of a rectifier 6.
  • the end stage If] in accordance with the invention, is allowed to 0perate with full emission, and this emission is controlled downwards.
  • the procedure is the reverse upon the reception of negative transmitters. In this way the entire length of the characteristic is always available for the image.
  • Fig. 3 there is shown the circuit for positive reception.
  • a grid bias therefore, is unnecessary, and the leak resistance 3 is connected to the cathode (if the plate potential is not selected to be too high).
  • the output valve I0 is a five-electrode tube.
  • the potentiometer l with coupling condenser 9 and the rectifier 6 are connected as described above. It is possible by adjustment of potentiometer I so to adjust the signal output of ID at the working resistance 4, which is directly connected galvanically to the Braun tube l2, that the synchronisation peaks produce exactly on the stationary value and never depart from the same, irrespective of the character of the image modulation.
  • detector Owing to the possibility of employing a condenser coupling 2 to the detector II and the working resistance l3 it is now possible to provide the detector with a sufiiciently high plate potential, so that it never flattens off by reason of insufficient plate potential, even under powerful excitations.
  • detector a grid-controlled twin grid three-electrode tube, which is already known for the reception of images having a large number of lines'and has the advantage that on the one hand it supplies, as compared with the twoelectrode tube, low-frequency amplification, and that on the other hand it eliminates itself the carrier Wave of the image.
  • the rectifier M can be applied galvanically with fixed bias [5 to the output, and in this way the synchronisation signals can be separated from the impulse-mixture independently of the particular image modulation by way of transformers l6, ll which are tuned each one to difierent frequencies (lineand frame-synchronisation signal).
  • the synchronisation is operative in an amplitude range defended by the bias regulated by the means I and I5.
  • the output tube I is furnished with a negative bias up to the point of disappearance of the emission and the polarity of the synchronisation rectifier I4 is also changed, another bias l5 being necessary. It is advantageous in practice to unite the two rectifiers B and M in a common bulb to form a twin-diode.
  • the synchronisation can also take place in very simple fashion by connection of the transformers I6, I! at the points l6a, Ila, i. e. in the circuit of the reaction coupling rectifier 6. Current only flows in this circuit when the cathode of B is at times negative in relation to the anode of 6. In all remaining cases the lead to the rectifier 6 is Without current. This, however, is just the condition for the passage of extreme negative impulses of the signals, i. e. for the synchronisation impulses themselves. In this manner it is possible to dispense with a special rectifier H! for the synchronisation.
  • a television amplifier system with resistance-capacity coupling means comprising at least i one tube having at least an anode, grid and cathode connected together as to form an input and output circuit with suitable biassing means, an additional circuit between said output and input circuit, said additional circuit including a rectifier tube in series connection with an ohmic potentiometer resistance and a condenser, said potentiometer with its tapping being adjusted in accordance with the amplification factor V so that a constant state of the signal peak potential is attained, said rectifier tube in case of positive television transmission being connected with its anode to the grid of said amplifier tube and with its cathode to the tapping of said potentiometer resistance, said potentiometer resistance being connected with its one terminal via said condenser to the anode of said amplifier and with its other terminal to said biassing means.
  • a television amplifier system with resistance-capacity coupling means comprising at least one tube having at least an anode, grid and cathode connected together as to form an input and output circuit with suitable biassing means, an additional circuit between said output and input circuit, said additional circuit including a rectifier tube in series connection with an ohmic potentiometer and a condenser, said potentiometer with its tapping being adjusted in accordance with the amplification factor V so that a constant state of the signal peak potential is attained, said rectifier tube, in case of negative television transmission, being connected with its cathode to said grid of said amplifier tube and with its anode to said output anode of said amplifier tube via said potentiometer and said condenser.
  • a television amplifier circuit comprising a source of signal energy, a first thermionic tube adapted to be energized by said energy, a thermionic output tube, a capacity-resistance means to energize said second tube from the first tube output, said output tube having at least a cathode, a control electrode, and an output electrode, means for applying a biasing voltage of a predetermined value relative to the cathode to said control electrode, a seriesconnected condenser and resistor element connected between the out put electrode and the biasing means, and a unilateral conductor element connected between a point on said resistor and the output tube control electrode so that a supplemental voltage may be applied to the control electrode of the tube to maintain a predetermined and substantially fixed output voltage from the output tube for peak value input signals, and a load circuit connected to receive the output energy from said output tube.
  • said unilateral conductor comprises a diode having its anode connected to said point on said resistor and its cathode connected to said control electrode so that the input signals may be received with increasing amplitude representing black in the television image.
  • said unilateral conductor comprises a diode having its cathode connected to said point on said resistor and its anode connected to said control electrode so that the input signals may be received with increasing amplitude representing white in the picture.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Circuits Of Receivers In General (AREA)
  • Picture Signal Circuits (AREA)
US179566A 1936-12-16 1937-12-13 Amplifier arrangement for television purposes Expired - Lifetime US2227026A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE499538X 1936-12-16

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US2227026A true US2227026A (en) 1940-12-31

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US179566A Expired - Lifetime US2227026A (en) 1936-12-16 1937-12-13 Amplifier arrangement for television purposes

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US (1) US2227026A (en(2012))
FR (1) FR832177A (en(2012))
GB (1) GB499538A (en(2012))
NL (1) NL54199C (en(2012))

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2547648A (en) * 1946-01-25 1951-04-03 Hazeltine Corp Automatic contrast control system for television apparatus
US2572179A (en) * 1949-05-24 1951-10-23 Philco Corp Peak leveling circuit
US2598929A (en) * 1949-12-15 1952-06-03 Philco Corp Direct current reinsertion circuit
US2672505A (en) * 1950-06-13 1954-03-16 Avco Mfg Corp Black level shift compensating amplifier
US2708687A (en) * 1949-05-10 1955-05-17 Motorola Inc Combined direct current reinserter and synchronizing pulse separator
US2800528A (en) * 1949-06-23 1957-07-23 Du Mont Allen B Lab Inc Video amplifier bridge circuit for minimizing supply voltage variations

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2515763A (en) * 1948-10-22 1950-07-18 Gen Electric Direct current restoration circuit for television

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2547648A (en) * 1946-01-25 1951-04-03 Hazeltine Corp Automatic contrast control system for television apparatus
US2708687A (en) * 1949-05-10 1955-05-17 Motorola Inc Combined direct current reinserter and synchronizing pulse separator
US2572179A (en) * 1949-05-24 1951-10-23 Philco Corp Peak leveling circuit
US2800528A (en) * 1949-06-23 1957-07-23 Du Mont Allen B Lab Inc Video amplifier bridge circuit for minimizing supply voltage variations
US2598929A (en) * 1949-12-15 1952-06-03 Philco Corp Direct current reinsertion circuit
US2672505A (en) * 1950-06-13 1954-03-16 Avco Mfg Corp Black level shift compensating amplifier

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Publication number Publication date
GB499538A (en) 1939-01-25
FR832177A (fr) 1938-09-22
NL54199C (en(2012))

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