US2375551A - Impulse amplifier - Google Patents

Description

May 8, 1 945.

SOURCE O F IMPULSE S c. E. HALLMARK 2,375,551

IMPULSE AMPLIFIER Filed March 18, 1943 CONTROLLED I8 APPARATUS INVENTOR HALLMARK Patented May 8, 1945 UNITED STATES PATENT OFFICE IMP LSE AMPLIFIER Clyde E. Hallmark, Fort Wayne, Ind., assignor to Farnworth Television and Radio Corporation, a corporation of Delaware 7 Application March 1a, 1943, Serial No. 479,567

, a 6 Claims. (01. 178-75) This invention relates to electronic amplifiers and particularly to apparatusadapted to amplify unidirectional impulses such as those employed in television systems.

' According to conventional practice in television systems, unidirectional impulses are used fora number of diflerent purposes. Typical uses for the receiver the synchronizing impulses must be separated from-thevideo signals of a composite television signal includingboth types of signals. Frequently the separating and amplifying functions are performed by the same apparatus.

' As is well understood in the art, however, where I a relatively high overall amplification of the ,im-

pulses .is'required, several amplifying stages may be needed. When high level positive output pulses are required the efliciency of such apparatus from a power consumption standpoint is quite low.

An object vof the presentinvention' therefore,

is to. provide a novel multi-stage amplifier which is capable of a large output and which has a high overall power efliciency. i

Another object of the invention is to provide novel means for separating the synchronizing impulsesfrom the video signal portion of acomposite television signal.

A'further object of the inventionis to provide a sourceofpolarizing potential to be applied to the anode circuit of a driving stage and derivable from an electrode of the driven stage.

In accordance with the present invention, there is provided a multi-stage amplifier, Each amplisynchronizing impulses is impressed upon the infier stage includes an electronic device having an input and an output circuit. Theimpulses to be amplified are impressed upon the input circuit of the first amplifier stage and the amplified impulses are derived from a load impedance included in the output circuit of a succeeding stage.

There is provided as part of the load impedance, an integrating circuit which is adapted to translate the impulsive energy applied theretofrom' the output circuit of the succeeding stage into a substantially constant unidirectional voltage.

This voltage is applied as a polarizing potential to the output electrode of thefirst stage. For this purpose a, conductive coupling is provided between the integrating network and the output electrode of thefirstamplifier stage. i

There are developed, in. the coupling, voltag varyinsinresponse to current changes in the output circuit of the first stage. These-current changes result from the impedance variation of the electronic device under the. control of the impulses applied to the input circuit thereof. These developed voltages are applied to the input circuit of the succeeding stage to efiect a control thereof, whereby amplified impulses are produced in the output circuit of this stage. A portion of the energy of theamplified impulses is used to maintain the voltage developed ,by the integrating circuit and the remainder may be used for a control purpose.

The connection between the conductive cou--.

cathode potential normally is sufiiciently negative to' effect cut-off of anode current. The currents representing the impulses in the ouput circuit of the first stage effect the development in the coupling of voltages which, when applied to the input.

circuit of the succeeding stage, render the electronic devicethereof conducting. Thus, if a composite television signal including video signals and put circuit of the first stage, the electronic device of the succeeding stage is rendered unresponsive to jsignals having the relatively small voltage amplitudes of the ,video signals. It is only when the signal amplitude increases to represent a synchronizingimpulse that the electronic device of the second stage responds to amplify such asignal. I Thus, the devicein accordance with themstant invention not only operates as a more efi'icient amplifier but also may serve as a, means for separating the synchronizing impulses from the video signals in a television syste For a. better-understanding of the invention together with other and further objects thereof, reference is had t the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appende claims.

In the accompanyingdrawing, the single figure is a circuit diagram of an amplifier embodyin the instant invention in what at present is con sidered a preferred form. Referring now more particularly to the drawing, there is shown a source of impulses I. This source may be a generator of periodic impulses.

of the tube is shunted by a grid leak resistor 4. The screen grid of the tube 3 is connected through a resistor 5 to a source offpositive direct current Voltage, such as a battery 6, and is bypassed to ground through a condenser 1. The

suppressor grid. of the tube is connected directly to ground so that it is maintained at the cathodepotential. The anode of the tube 3 is connected to a source of positive'potential which will be described more fully hereinafter.

The second stage of the amplifier includes an output or driven vacuum tube 8, the anode of which is connected directly to the positive ter-' minal of the battery 8. The screen grid of the tube 8 is connected through a resistor 9 to the battery 6 and is also bypassed to the cathode through a condenser II]. There is-also provided a resistor II for establishing a desired potential on the screen grid of vacuum tube 8. The cathode of the tube 8 is connected to a load impedance which includes a resistor 12 and an integrating or energy storage network I3. The integrating network comprises the parallel arrangement of a resistor Hi and a condenser l5 and is connected between the resistor l2 and ground. The cathode of the tube 8 is also connected through a coupling resistor Hi to the anode of the tube 3. The coupling resistor also serves as the load for the output circuit of the tube 3. The controlgrid ofthe tube 8 is connected to the anode end of the coupling resistor [6. j r

The output circuit for the amplified impulses is derived from the terminals of the load impedance of the tube 8. This circuit is coupled by a condenser I! to the apparatus l8 which is. to be controlled by the impulses.

Referring now to the operation of the system, assume that there is applied to the input circuit of the tube 3 a series of unidirectional impulses of such polarity that the grid-to-cathode potential of this tube is decreased thereby. As a result of the repetition of these impulses in the output circuit of the tube 8 impulsive energy is applied to'the integrating network I3. The time constant of. thiscircuit is such that there is maintained at the terminals thereof a substantially constant unidirectional voltage. This voltage maintains the cathode of the tube 8 at a relatively high decreases The resultant decrease of the voltage .drop across the coupling resistor I8 is siiflicient to raise the grid-to-cathode potential of the tube 8 to the point where this tube becomes conducting. Thus, it is seen that there is repeated in the output circuit of the tube 8 the signal hich exists in the input circuit of the tube a. Each of the amplified impulses repeated in the output circuitof the tube 8 produces sufficient appliedtothe input circuit of the tube 3, are of first stage of the amplifier. The input circuit insufilcient amplitude to cause the anode current in this tube to approach cutoff, thus tube 8 remains biased to or beyond cutoff and no variations in the output current of tube 8 occur. Video signals, therefore, are not repeated into the out-. put circuit of the second amplifier stage; However, the.amplitude.0f the synchronizing signals is suflicient to reduce the anode current of the tube 3tothe point where the tube 8 becomes conducting. The synchronizing signals then are repeated in the output circuit of the second amplifier stage. Consequently, it is seen that the apparatusin accordance with the present invention will function as a separator of the synchronizing signals from'the video signals in a television system.

While it will be understood that the circuit specifications of the amplifier may vary according to the design for any particular application, the following circuit specifications for an amplifier employed for either of the applications described are included by way of example only:

The amplifier in accordance with the instant invention has a number of desirable and advantageous features. The output voltage supply for the first amplifier stage which is taken-from energy stored in the output circuit of the second stage results in a substantial increase in the overall efliciency of the amplifier from the standpoint of power consumption. The derivation of. the

acteristic of the amplifleris its capability of producing a relatively large output.

While there has been described what, at present, is considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and therefore, it is aimed in the appendedclaims to cover all such changes and modifications as fall within. the true spirit and scope of the'invention.

What is claimed is: 1. In an electronic amplifier, a first stage having iiiput and output circuits, a second stage having input and output circuits, an energy storage circuit including an integrating network 'connected in the output circuit, of said second stage, means for energizing the output circuit of said first stage from said storage circuit, and means for deriving from said energizing vmeans a.contr0l ,put 'circuitoi. said second stage.

voltage for the input circuit of said second stage,

whereby to reproduce in the output circuit of said I second stage signals impressed upon the input,

circuit of said first stage. g

2. In an'electronic amplifier, an output electronic device having input and output circuits,

, trol voltages upon said input circuit of said output electronic device, whereby said signals' are reproduced in the output circuit of said output electronicdevice to energize said storage network.

3. In a two-stage amplifier, a coupling arrangethe output circuitof the second' stage including an integrating circuit, means for deriving from said integrating circuit a substantially constant cuit of the first stage, andmeans for deriving from said coupling means a control voltage for the in- .4. An impulse amplifier comprising, an input vacuum tubehavirig a control grid. and an anode, I means for impressing impulse voltage upon said grid to produce related impulse voltages at said anode, an output vacuum tube having a control grid and a cathode, a-load impedance including an integrating network, means including said network for maintaining said cathode at a substan-' ance with variations of the anode voltage 017 said input tube in a manner to eifect the repetition by said output tube of impulses to said network.

5. 'Apparatus for amplifying signal impulses v comprising, adriving vacuum tube having input and output circuits, said output circuit including an anode, a driven vacuum tube having input and output circuits, said input circuit including a cathode and a control" grid, a load impedance for the output circuit of said driven tube including an integrating network connected to said cathode, a load impedance for the output circuit of said driving tube including a resistor connected I ment between the stages comprising a load for r-unidirectional voltage, means for coupling said v unidirectional voltage to supply the output cirbetween saidcathode and said anode, means for coupling said grid to said anode, means for impressing voltage impulses of negative polarity upon the input circuit. of said driving tube, whereby to produce amplified voltage impulses of positive polarity in the output circuit of said driven tube, said integrating network utilizing said positive impulses to produce a substantially constant supply voltage for the output circuit of said driving tube.-

6. Apparatus for separating synchronizing impulses from a composite television signal including video signals and synchronizing impulses comprising, a vacuum tube having input and output circuits and arranged to reproduce in said output circuit a composite television signal impressed upon'said input circuit, a second vacuum tube having input and output circuits, said second tube output circuit including a series 'arrangement of a source of unidirectional energy and an energy storage network, an impedance element connected to the input circuit of said second tube, said impedance element also serving to couple said energy storage circuit to the output circuit tially constant unidirectional potential, means including a conductive coupling to impress said unidirectionalpotential upon the anode of said in put tube-and means for deriving from said coupling-a control voltage for the grid of said outputtube, said control voltage varying inaccordof "said first tube, wherebysaid reproduced composite television signal develops corresponding voltages-in said impedance element, and means including said impedance element for biasing the input circuit of. said second tube so as to render the output circuit thereof responsive only to the developed voltage representing the synchronizing impulses.

Images