US2853607A - Integrating amplifier - Google Patents

Description

Sept. 23, 1958 M. A. ALEXANDER 2,853,607

INTEGRATING AMPLIFIER Filed Aug. 25. 1954 '0 TRIGGIR- 0Y6 SAG/Vii JOURCE By Agog/70% ATTOR/VEIS The anode voltage slowly decreases in value.

United States PatentD INTEGRATING AMPLIFIER Matthew Arnold Alexander, Pacific Palisades, Califl, as-

signor, by mesne assignments, to Telemeter Magnetics and Electronics Corporation, Los Angeles, Caiifl, a corporation of New York Application August 23, 1954, Serial No. 451,383 5 Claims. I (Cl. 250-27 This invention relates to electronic amplifier networks and more particularly 'to an improvement in electronic integrating networks. Integrating networks find extensive use in present-day electronic systems as components in analogue computers. Furthermore, in view of the substantial linearity of their output wave shape, they also find extensive use for the provision of accurate timing wave shapes. The Miller integrator usually consists of an electron discharge tube with its anode connected back toits grid by way of a condenser. This negative feedback is provided to the grid. Input signals are applied to the grid through a resistor. In operation, the integrator tube is biased in the conducting region. A positive input to the grid increases the tube anode current. The longer the duration of'the application of the positive impulse, the more toward conduction a tube is driven. The negative feedback from -the anode prevents instantaneous conduction but makes this a function of the values of input resistor and feedback condenser and the duration of the application of the positive input pulse. The wave shape obtained from the anode is essentially a time integral of the input signal. For a given constant input voltage signal the slope of the voltage output curve is substantially constant. In order to insure isolation between the integrating tnbe and its output load, a cathode follower may be employed in the feedback loop. The output from the anode of the integrator tube is applied to the control grid of a cathode-follower tube. The integrating condenser couples the cathode-follower cathode with the control grid of the integrator tube. Output is taken from the cathode-follower cathode. It will be appreciated that the higher the gain of the integrator tube, the greater the feedback voltage for a given signal and the more linear will be the output wave shape and the less the possibility for variation thereof with variation of the circuit components.

An object of the present invention is to provide a novel high-gain integrating network.

High gain may be achieved by increasing the anode load of the integrator tube. However, this has the disadvantage of requiring a high value of anode load supply voltage.

Accordingly, another object of the present invention is to increase the gain of an integrating circuit by increasing the effective value of the anode load resistance and anode supply voltage.

Still another object of the present invention is to provide a novel, simple, and stable high-gain integrating circuit.

These and other features of the invention are achieved in an integrating circuit of the type employing a cathode follower in its feedback loop by using a voltage regulator tube or tubefilled with inert gas which is connected between the cathode of the cathode follower and a tap on the anode load circuit.

The novel features that are considered characteristic of this invention are set forth with particularity in the ap- A ice grid 14, cathode 20, screen grid 16, and suppressor grid I 18. An operating voltage supply is provided. A voltage divider 22 is connected across the voltage supply for the purpose of providing a voltage for the screen grid'1 6 which is connected to it. This is maintained relatively low. The suppressor grid 18 maybe utilized for maintaining the first tube cut off until it is desired to operate the integrator network for which purpose it may be connected to a source of triggering signals. Otherwise, it

may be connected to ground. The cathode 20 of the first tube is connected to ground. The anode 12 is connected through two series-connected anode load resistors 24,

I which may also be a single anode load resistor 24 with a tap, to the source of operating voltage. A second tube 30, which is a cathode-follower tube, has its control grid 32 directly connected to the anode 12 of the first tube. Its anode 34 is connected to the source of operating potential and a cathode load resistor 38 connects its cathode 36 to a source of negative bias. A feedback condenser 40 connects the cathode-follower cathode to the control grid of the integrator tube. An input signal is applied through an input resistor 42 which is connected to the control grid 14.

As thus far described, this system is a well-known type of integrator with feedback using a cathode-follower tube. As the anode of the first tube goes positive or negative in response to an input signal, a corresponding positive or negative voltage is fed to the first tube control grid through the cathode-follower tube and the coupling condenser. The theory of these integrating networks may be found described, for example, in chapter 4 of the book Electronic Instruments by Greenwood et al., published by McGraw-Hill Book Company.

With a given power supply and tube type, in order'to increase the tube gain or the change of voltage at the anode in response to a change in the signal applied to the control grid, the value of the anode load resistor is increased. Thereby, changes in current drawn by the tube as a result of the signals applied to the control grid pro duce larger voltage changes at the anode. However, a point of diminishing returns is rapidly approached, since the increased anode load resistor lowers the voltage available at the tube anode. Accordingly, the tube draws less current and the gain is actually less than more. With the present invention, an increase in the gain available from the first tube is secured by connecting a gas-filled diode or neon-glow tube which is generically referred to here as a voltage-regulator tube 50 between the tapped anode load resistor 24 and the cathode 36 of the cathodefollower tube. The tapping point is selected so that the potential across the tube exceeds its required ignition voltage. The anode 52 is connected to the anode load resistor and the cathode 54 is connected to the cathodefollower cathode. This has the effect of making the gain of the system exceedingly high. This will be seen from the following explanation of the operation of the invention.

Assume, for the purposes of explanation, that the voltage at the anode of the tube is volts. The voltageat the junction of the two anode load resistors is 187 volts, there being an 87-volt drop across the lowermost portion of the load resistor as a result of the current flowing through the first tube. The voltage applied to the grid of the cathode follower is substantially 100 volts,

and the voltage at the cathode of the cathode follower may be a few volts more than this value. Accordingly, the voltage being applied to the control grid of the tube is also substantially 100 volts. The voltage across the. voltage regulator tube is essentially 87 volts, which is sufiicient to make it conductive. Assume a signal is applied through the input resistor to the control grid o the integrator tube, which causes the tube to draw more current. Assume that this signal causes, a lO-volt drop at the anode of the first tube. to occur at the grid of the cathode follower and substantially a IO-volt drop at the cathode of the cathode follower. Since there is a constant voltage drop across the regulator tube, there occurs a 10-volt drop at the junction of the two anode load resistors. There is a 10-volt drop. if (1) the gain of the cathode follower is unity and (2.) the efiective resistance of the regulator tube is zero. The effect of (1) a finite regulator impedance, (2) a gain of less than unity in the cathode follower, and v(3) the finite impedance of the tube 10 is to reduce the value of the, voltage fed back to the junction of the two anode resistors. The change in current in the section of resistor 24 between the plate of tube 50 and the plate of tube 10- has been decreased from the value without this form of positive feedback to a value where A is, a number which primarily specifies the gain of the cathode follower. The value of A may approach one very nearly say .99. Using this value of A as an example, the efiective value of R has been increased by 100 times and the effective potential applied to R has been increased 100 times. The circuit behaves similarly if the input voltage is such as to cause an increase of Voltage at the anode.

Therefore, the effect of the connection of the voltage regulator tube into the integrator network is to provide an extremely high-gain integrator network with-out increasing the first tube anode load resistor, without increasing the voltage from the power supply or changing the type of tube used. Despite the large amount of positive feedback, there is no oscillation since, in view of the cathode follower, the feedback loop gain is less than one, although the system gain is extremely high, gains on the order of 100,000 having been achieved.

Thus, with a simple expedient, this invention achieves a novel, useful, and simple high-gain integrating network that can provide a very stable and linear output in response to an input signal.

I claim:

1. In an electronic integrator of the type having a first tube including an anode and a control grid, an anode load resistor connected to said anode, a feedback network between said first tube anode and control grid including a cathode follower tube having a control grid and cathode, said control grid being connected to said first tube anode, and a condenser connected between said cathode-follower This causes a 10-volt drop a cathode and said first control grid, the improvement consisting of a voltage regulator tube connected between a point on said anode load resistor and said cathode-follower cathode.

2. In an electronic integrator as recited in claim 1 wherein said voltage regulator tube has an anode and cathode, said anode being connected to the tapon said anode load resistor and said cathode being. connected to the cathode of said cathode follower tube.

3. An electronic integrating network consisting of a first and a second tube each having anode, cathode and'control grid electrodes, means connecting said first tube anode to said second tube control grid, a cathode load resistor connected to said second tube-cathode, an anode load resistor connected to said first tube anode, a condenser connected between said second tube cathode and said first tube control grid, a signal input resistor connected to said control grid, and a voltage regulator tube connected between a tap on said anode load resistor and said second tube cathode.

4. The combination with an electronic integrator of'the type having a first tube including an anode and a control grid, an anode load resistor connected to saidanode, a feedback network between said first tube anode and control grid including a cathode-follower tube having a control grid'and cathode, said control grid being connected to said first tube anode, and a condenser connected between said cathode-follower cathode and said first tube control grid, of a voltage regulator tube having an anode anda cathode, said voltage regulator anode beingc'onnected to a point on said anode load resistor, said voltage regulator cathode being connected to said cathode-follower cathode.

5. An electronic integrating network consisting of a first tube having an anode and a control grid, an anode load resistor connected to said anode, and a feedback network between said anode and said control grid, said feedback network including a cathode-follower tube, said cathode-follower tube having a cathode and control grid, said cathode-follower tube control grid being connected to said first tube anode, said cathode-follower tube cathode; being coupled to said first tube control grid, a voltage-regulator tube having an anode and a cathode, said voltageregulator tube cathode being coupled to said cathode-follower tube cathode, and said voltage-regulator tube anode being connected to a point on said first tube anode load resistor the potential at which exceeds the potential at said cathode-follower grid by an amount sufficient to render said voltage-regulator tube conducting.

References Cited in the file of this patent UNITED STATES PATENTS 2,554,172 Custin May 22, 1951 2,562,792 James July 31, 1951 2,581,456 Swift Jan. 8, 1952 2,642,532 Mofenson June 16, 1953 2,651,719 White Sept. 8, 1953. 2,662,981 Segerstrom Dec. 15, 1953 2,678,391 Lappin May 11, 1954 2,691,728 Noble et al. Oct. 12, 1954 2,701,306 Bess Feb. 1, 1955 2,769,904 Ropiequet Nov. 6, 1956

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