US2673929A - Integrating circuit - Google Patents

Description

March 30, 1954 c. AN 2,673,929

INTEGRATING CIRCUIT Filed July 27, 1951 Fig. l

66 68 73 KIZ 2% I I I I I I 78 76 v I I I I I I I I w lu I I I I I XE I 72 74 I I 1 I ee I ,58 D gI7 7- o 77 77 TIME INVEN TOR. CHARLES E. HUFFMAN BYfiAXAGL A TTORNE YS Patented Mar. 30, 1954 INTEGRATING CIRCUIT Charles E. Hufiman, Upper Montclair, N. .L, as-

signor to Allen B. Du Mont Laboratories, Inc., Clifton, N. .L, a corporation of Delaware Application July 27, 1951, Serial No. 238,991

Claims. 1

This invention relates to electric integrating circuits which function to produce an output signal, the magnitude of which is periodically controlled by a series of input pulses.

A use for integrating circuits is described in U. S. Patent No. 2,530,431, entitled "Color Device for Utilizing Control Signals. In that patent, pulses derived from a television picture tube at the end of horizontal sweep lines of the electron beam are fed into the integrating circuit. The output of the integrating circuit provides a responsive signal of longer duration than that of the input pulse, said duration corresponding to the time required for the next succeeding one or more horizontal sweep lines. Said output signal is utilized to affect the vertical deflection of the electron beam in order to secure accurate registration of the horizontal lines.

Objects of the present invention are to provide an integrating circuit which will accommodate both positively and negatively polarized input pulses, which will accurately maintain a constant level of output voltage after each input pulse and until the next input pulse occurs, which will quickly reset when desired, which has improved linearity of response, and which has improved response to signals of small magnitude.

Figure 1 is a partial block-and-schematic diagram of a circuit embodying the invention.

Figure 2 is a graph showing the time correlation of signals appearing in various portions of the circuit.

In Figure 1, a source ll of input pulses I2 is connected to an anode l3 and a cathode [4 of a dual diode tube l6 through capacitors l1 and E8. The remaining cathode 2| and anode 22 of the tube It are connected together, to an integrating capacitor 23, to a cathode 24 of a first triode tube 28, to an anode 21 of a second triode tube 28, and to an output terminal 29. An anode of the first triode 26 is connected to a source 32 of positive potential, of which the remaining terminal is grounded. A cathode 33 of the second triode 2B is grounded. The remaining terminal of the integrating capacitor 23 is connected to a filter capacitor 34 and to an adjustable contact 36 of a resistor 31. One end of the resistor 31 is connected through a resistor 38 to ground. The remaining end of the resistor 31 is connected through a resistor 39 to the source 32 of positive potential. The adjustable contact 36 is connected to the cathode M of the diode l6 through series resistors 4| and 42 and also to the anode l3 of diode I 6 through series resistors 43 and 44. A

resistor 46 is connected between the junction of,

said resistors 4| and 42 and the source 32. A resistor 41 is connected between the junction of said resistors 43 and 44 and ground. The control electrodes 48 and 49, of the triode tubes, 26 and 28, are connected respectively through resistors El and 52 to the cathodes 24 and 33, of said tubes and through capacitors 53 and 54 to a source 56 of keying signals 57. An output signal 58 occurs at the output terminal 29. The return path of the output signal 58 is provided through a grounded terminal 59. Return paths for the signal sources I I and 5E are provided by grounded terminals 6i and 62.

In Figure 2 the input signal [2, the keying signal 51 and the output signal 58 are represented together on a time axis. When the circuit is operated, a first input pulse 66 causes an output signal 61 to occur. A second input pulse 68 causes an incremental increase 69 in the output signal. A third input pulse ll of opposite polarity from the first two input pulses causes an incremental decrease 12 in the output signal. A further input pulse 13, having the same polarity as the first two pulses again causes an incremental increase 14 in the output signal 58, etc. When a keying pulse 16 occurs in the keying signal 57, the output signal is restored to its original steady magnitude 11. It is to be noted that the input pulses do not necessarily occur at regular intervals, as is indicated by the absence of a pulse at the time indicated by numeral 18 in the input signal it. Furthermore, said input pulses need not be of equal magnitudes.

The circuit operates as follows: The movable connection 36 of the resistor 31 is adjusted to obtain a desired value of bias voltage. The network, comprising resistors 45, 4| 43 and 41, provides operating voltages in conjunction with resistors 42 and 44 for the input cathode M and anode it of the dual diode tube !6. Said resistors, comprising the bias voltage-producing network, have values to provide a bias on the anode 13 which is negative with respect to the bias on the cathode M. The purpose of these bias voltages is to com pensate for a contact potential voltage inherent in the diode tube [6, so that the integrating capacitor 23 will be equally affected by positive or negative input pulses. The compensation also improves linearity at low signal levels. The bottom terminus of the integrating capacitor 23, being connected to the junction of resistors 4i and 43, biases said terminus at a potential intermediate that of the anode I3 and cathode M of the dual diode tube IS. The exact value of this bias may be controlled by adjusting the connection 36 of the resistor 31. In the particular circuit shown the ohmic values of resistors 46 and 41, 4! and 43, 39 and 38, and 42 and M, are respectively equal, thus providing a steady bias voltage on the two terminals of the integrating condenser 23 that is approximately one-half of the voltage of the potential source 32.

The pulses of the input signal 12, either positive or negative polarity, are passed through and rectified by the dual diode tube It and place increments of charge on the integrating capacitor 23. The capacitance of said condenser 23 is relatively large so that individual pulses of said signal [2 do not fully charge said condenser, but merely add or subtract increments of charge; i. e., if the integrator capacitor 23 is positively charged, then a positive pulse from the signal 12 will increase the positive charge by an incremental amount, and a negative pulse from the signal I2 will reduce said positive charge by an incremental amount. If the majority of said pulses have negative polarities, the charge on the capacitor 23 will be of negative polarity.

The triode tubes 26 and 23 function as discharge paths for the integrating capacitor 23. Said discharge devices 2 6 and 28 are normally non-conductive and the leakage path across the terminals of the integrating capacitor 23 is of a relatively high resistance so that the voltage charges on said capacitor will not leak off and will be affected only by incoming pulses from the input signal 12. When it is desired to completely discharge capacitor 23, a keying signal El is applied to the discharge devices 25 and 28.

Each of said keyed discharge devices 26 and 23 then becomes effectively a short-circuit path connected in parallel with the integrating capacitor 23, but with opposite polarities. Therefore, if said capacitor 23 is positively charged, when the discharge tubes are keyed said charge will discharge through the tube 28; if the charge on said capacitor 23 is negative, said charge will discharge through the tube 2%. The discharge paths include the resistors 32, 31, and 38. These resistors have relatively small values of resistance and do not materially affect or impedethe discharge of said capacitor 23 through said discharge devices.

As referred to in the above-mentioned issued patent, when the integrating circuit is used in connection with registration of electron beam scanning lines in a television picture tube the keying pulses 51 may conveniently comprise vertical blanking or synchronizing pulses from a television signal, so that, at the end of each picture scanning field, the output signal 58 is reduced to zero value. Thus, each new picture field is commenced with a zero value of output corrective voltage 58 as each successive horizontal scanning line occurs, any deviation from the desired scanning path causes signal pulses l2 to be generated, from which the integrator circuit of the present invention derives a corrective output signal 58, the value of which changes incrementally with further deviations from requiredregistry until the end of that particular field, whereupon said corrective signal 58 is restored to its initial zero value by the action of the discharge tubes 26 and 28.

Although the invention has been described particularly in connection with television apparatus, it may also be used for any application where its characteristics are desired.

What is claimed is:

1. An integrator circuit comprising. a source 4 of recurrent pulse signals, a first rectifier having an anode and a cathode, said anode being connected to said signal source, a first source of bias voltage connected to said anode, a second rectifier having an anode and a cathode, said cathode being connected to said signal source, a second source of bias voltage connected to said cathode of said second rectifier, a common connection between said cathode of said first rectifier and said anode of said second rectifier, a third source of bias voltage, a capacitor connected between said third source of bias voltage and said common connection, an output terminal connected to said common connection, a first and a second electron discharge device each having an anode, a cathode and a control electrode,

a connection between said anode of said first electron discharge device and said output terminal, a connection between said cathode of said second discharge device and said output terminal, a connection between said cathode of said first electron discharge device and the terminal of said capacitor connected to said third source of bias voltage, a connection between said anode of said second electron discharge device and said terminal of said capacitor connected to said third source of bias voltage, and a source of keying signals connected to said control electrodes.

2. The apparatus of claim 1, in which said third source of bias voltage is variable.

3. The apparatus of claim 1, in which said third source of bias voltage has a value intermediate the values of said first and second sources of bias voltage.

4. The apparatus of claim 1, in which said source of pulse signals comprise pulses having difiering polarities.

5. The apparatus of claim 1, in which said first source-of bias voltage is negative with respect to said second source of bias voltage.

6. The apparatus of claim 1, in which said connections between said first source of bias voltage and said anode and between said second source of bias voltage and said cathode comprise impedances having values to provide time constants in conjunction with said capacitor that are greater than the time of recurrence of said pulse signals.

'1. An integrator circuit comprising a source of pulses, a bi-directional conductive rectifier, and a capacitor connected in series, output terminals connected across said capacitor, a keyed bi-directional conductive discharge device connected across said capacitor, and a source of keying si nals connected to said discharge device.

3. An integrator comprising a duo-diode having two each of anode andcathode electrodes, means for applying biasing voltages to one of the anodes and one of the cathodes of said duodiode, a source of recurrent pulse signals connected to said last-named anode and cathode, an output circuit connected to the remaining anode and cathode electrodes of said duo-diode, a biased capacitor also connected to said remaining anode and cathode electrodes, means providing a normally non-conductive discharge path for saidcapacitor and a source ofkeying pulses for causing said last means to be. conductive at pie-determined intervals.

9. An integrator comprising a source of recurrent positive and negative pulse signals, an integrating capacitor, means for bi-directionally rectifying said pulsesand charging said capacitor with said rectified positive and negative pulses, normally non-conductive means for discharging said capacitor, a source of keying pulses for selectively rendering said discharging means conductive, and an output circuit ccnnected across said capacitor.

10. In the combination of claim 9, means for applying a biasing potential to said rectifying means and means for applying a biasing potential to said capacitor.

CHARLES E. HUFFMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date White Apr. 5, 1938 Farrington Dec. 31, 1946 Schoenfield Feb. 11, 1947 Smith, Jr Aug. 15, 1950

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