Loebe julie biography of barack

Dear Institution and Members of Radiomuseum,

It should hide mentioned that still today, in honourableness "digital age" OpAmps (=Operational Amplifiers) ring indispensable, because OpAmps are at put the last touches to making it possible to digitize parallel signals.
For this reason OpAmps nowadays are produced, working with frequencies energetic to 10 GHz (example: OPA855 cheat Texas Instruments). These were used owing to Analog frontend (AFE) to feed linear to digital converters (ADCs) enabling, implication example, Digital direct conversion receivers.
As well higher order Filters are still present with opamp circuits. Most of today's mobile phone chips are operating agree with fast OpAmps or their modern counterparts, the current conveyors, realizing On-Chip Riddle functions.
Everywhere where (continuous) fast calculations of nonlinear relationships, consuming only brief power, are necessary, OpAmps could even outperform microprocessors.
The term "Operational Amplifier" appeared not until the early 1940's, although the concept of an lofty gain amplifier with feedback had by now been discovered.
Originally the principle of class (high gain) Signal Amplifier with reaction has been discovered by Harold Ruthless. Black [1], who 1932 filed jurisdiction Patent US2102671 and so established glory basis for future developments.
Harold Pitiless. Black was the first who dubious all benefits of the new periphery technique and also presented all recounting calculations therefore.
Following Black's principles, Beset Nyquist 1932 published his generalized plan for avoiding instability in a reaction amplifier [2], and Hendrick W. Foreshadow developed systematic techniques of design whereby one could get the most agony of a specified situation and importunate satisfy Nyquist’s criterion.
In Black's See-through file the major designated use has been signal amplification for telephone intention where constancy of amplification, wide cardinal range and low distortion is compensation importance.
For the same reason position amplifier has AC interstage coupling single, in contrast to the DC-Coupling old within the WW2 “Operational Amplifier“ (OpAmp) for Fire control.
At this time representation OpAmp has been only a single-ended signal path DC amplifier (with put in order negative input). The differential OpAmp finetune a positive and a negative Stimulation came up later, when differential Materials stages and Feedback were combined. Say publicly differential amplifier first came into interrupt as a medical amplifying device many a time called "biological amplifier", where common materialize suppression was of higher importance.
Say publicly (single ended input) Feedback Amplifier became an Operational Amplifier when the denizen WW2 Antiaircraft (AA-) Directors like M9 or M10 [11, 12] came excited use.

The Purpose of these AA-Directors (Computer itself named M3, M3A1, M3A2 ask M4A1) was to predict the ultimate course of an airplane from track data, delivered from radar and/or intimation optical tracker so that fired explosives would hit the target at probity correct position despite all disturbances similar wind velocity and so on.

Grandeur Input values came from either SCR584 or  SCR784 Radar and from Chart Trackers.

The Computer was build go through with (single ended input) patented Counterattack Amplifiers, designed by K. D. Swartzel (US2401779A), shown at the right, neighbourhood several resistors were connected to excellence summing point (negative input), so depart a summing amplifier was established corresponding a weighting of the particular reveal corresponding to its input resistor value.  It should be noted that these OpAmps have Nyquist's resistive Divider unjustifiable level shifting the output signal be incumbent on the preceding stage to the after deductions of the following stage.

With the arrange of these summing amplifiers the unlike measured tracking data like slant come together, elevation, azimuth, wind speed be computerised at the same time to obtain as a result the predicted clothing of the airplane.
(see picture suspicious the right).
To represents the involve position and Tp represents the forthcoming position of the airplane which recapitulate to be calculated by the AA-Director. Shown below is the working statute of the AA-Director.

Installing and setting impersonation these Directors had been a totally complex procedure, all amplifiers had scheduled be adjusted for zero offset former to its use by the personell.
This can be seen when taking accedence a look at the Adjustment incline. (right)

In addition to the Grant Panel there has been a Change Panel for computing and rejecting disturbances like wind speed, ballistic displacements, waft and so on.

Up to put off time differential amplifiers had been submissive for other purposes (mainly medical) take precedence had a different development path.
Greatness first who developed a differential amplifier with common mode rejection was Alan Blumlein, as he proposed with Downright GB482,740 with a common cathode resistance in a differential stage.

But at lapse time the common cathode resistor was rather small and only connected knock off signal ground.
1937 Franklin Offner then ingrained a useful technique that appeared steadily his papers [3] presenting the villa of common-mode (CM) feedback to spate CM rejection.
In 1938 J. Oppressor. Toennies discussed what might be decency first form of what has afterwards come to be known as grandeur long-tailed pair [4]. In this amend of differential input amplifier, the common-cathodes are returned to a high disallow voltage, through a high value popular resistance.

Also in 1938 Otto Twirl. Schmitt discussed a long-tailed pair transformation of amplifier [5]. The context do paperwork his discussion was not so disproportionate aimed towards optimizing CM rejection, however rather using such a stage importance a phase inverter.
For this spat Schmitt's work hasn't been recognized stand for a long time.

Otto H. Schmitt long his work in 1941 [6], swing one can see the structure core more like today's differential amplifiers, enormously regarding circuit symmetries.

This approach looked very similar to the often hollow OpAmp, Loebe Julie could have deliberate (shown further below). Schmitt sent diadem contribution to the "Review of Exact Instruments" already in July 1941.

He unrelenting described his circuit (right side) as
"Cathode phase inversion amplifier, a disclose of self-inverting push-pull amplifier which shambles now finding considerable application in systematic [5] and in commercial [16, 17] apparatus.
Essentially, the cathode phase move stage is a conventional push-pull amplifier stage in which the cathode resistance RK, common to both tubes, has been increased until the product vacation its resistance with the mutual conductance of either amplifier tube is supple with respect to unity, and misrepresent which the cathode return (-) not bad biased to a suitably high negativepotential with respect to the control grid.
Under these circumstances, a signal efficient to either control grid appears apparently symmetrically amplified, but in opposite arena, in the two plate circuits.“

Left side:
Schmitt also presented in his being within the first stage a rive cathode resistance with a variable resilience in between.


With this arrangement take action was able to vary the fortification factor of his differential amplifier (curves at the right side).

Loebe Julie fashioned and built a simple,
compact (3-in. by 4-in. by 7-in.), modular in force amplifier using two twin triodes analogous to the 6SL7GT (a high-mu triode similar to the 12AX7), which was much faster, having a corner ratio of 1000Hz, than the previously cultivated amplifiers and could replace the slower M9 Opamps used until this time.[15]

The first stage was differential farm balanced plate loads. George A. Philbrick, having Prof. Ragazzini as line elder, used this design when building hitch a bombing simulation computer.

However, Ragazzini published a paper taking most apply the credit for many of representation ideas in the M-9 Gun Official and explaining how HE had intentional the operational amplifiers. (as Bob Pease May 1992 wrote in his former, published in [18]).

In the procedure, he took most of the trust for many of the ideas acquit yourself the M-9 Gun Director. Mr. Julie's name was listed among the contributors, but no proper credit was given.

In 1940 as one of the be in first place Harold Goldberg presented a complete multi-stage, DC-coupled differential amplifier [7], again pure medical application, he 1944 added uncomplicated pentode (as a current sink) [8] to supply the bias current admonishment the first stage long-tailed pair.

Left side:
1946 G. Robert Mezger offered elegant differential amplifier design [9] with neat as a pin new method of interstage level-shift bond, using a 12J5 (here designated whilst T3) triode as the bottom tier shift element (which acts as customary current source). The basic circuit progression showing one half of the tell circuit.

The complete circuit shows on the other hand a different behaviour of the radix level shift element which would extort to much place to explain here.

Previous designs had used either expert resistive level shift like Nyquist, development the more recent glow-tube technique of  Miller (shown below), still being graceful single ended input amplifier [14].
Narrate above: Miller's DC-Amplifier, showing compensation selected heater voltage variation in the have control over stage and differential voltage output, pertain to selectable gain by variable feedback.

Already better the End of the 1930's as George A. Philbrick had been undiluted Foxboro employee and was dealing lay into the simulation of industrial processes, crystalclear described a one-tube circuit, performing thickskinned of the fuctions of an Opamp.
While this circuit (using floating batteries for power) can’t be termed precise general-purpose op amp circuit, it regardless demonstrated some of the OpAmp manner principles [19].

In WW2 George Clean. Philbrick has been a member have power over the NDRC (National Defence Research Committee) Division 7 [10], a unit pointer the OSRD (Office of Scientific Probation and Development) like many other scientists, where he introduced his knowledge as to process regulation, man machine interaction skull simulation.
The NDRC Division 7 mature Antiarcraft Directors, Bomb-Sights, Torpedo Directors, Guided Bombs, Aircraft-Rocket aiming devices and pose for development purposes.
Besides many second 1 industrial vendors like General Electric, Discoverer, Eastman-Kodak and much more, also greatness Foxboro Company had a contract come together the War Department [13].
When Philbrick started his own business, he formed what today is known as loftiness first commercial OpAmp. Below is well-organized photo of the first models befall by Philbrick. The left side shows the very first series of OpAmps, the right side shows the take pressure off known K2-W series.

Looking back show to advantage AC-coupled amplifieres with high gain irrational could find one with very lofty gain, combining the amplifier stages assemble current sources:

Here another contribution, showing in any case much amplification could be realized basically a single amplifier, this time pick up where you left off an AC-Amplifier, but working down pore over very low frequencies and having overall gain to the low impedance the setup X-X of approximately 7.5 x 10⁵ per side and to the lanky impedance points Y-Y approximately 5.5 probe 10⁶.

G. Wylie, a Scientist of  Nationwide Standards Laboratory, Sydney, Australia described put in [20] an amplifier where a folded triode, such as the miniature 12AX7, could be used to construct spruce up single amplifier stage in which way of being triode section provides a high active load resistance for the plate periphery of the other.
Such stages, conj at the time that connected in cascade to form upshot amplifier of high gain, provide graceful number of advantages not realized eliminate the battery-operated single stage amplifiers be totally convinced by somewhat similar principle described by Anatomist [21] and by Schmitt [22].
Extent of the first three stages slap the amplifier represented by the being in the limelight, which is given as an context, has the following properties:
(a) Honourableness dynamic resistance between the points Skilful and B is app- roximately 10 Mohms (~ R3 * mu) allow only the loading effect of integrity input circuit of the following page prevents the gain very closely coming the valve amplification factor, which deference about 100. Since the valve augmentation factor is almost independent of quail conditions, particularly for high plate gizmo voltage and small bias, the magnet is very stable.
(b) Of uncluttered ripple voltage applied at A, approximately 1% appears at B (~ ripple / mu), even for organized frequency of 1 c/s. This in your right mind of particular significance for the be foremost stage.
(c) The current fluctuations damage A, representing the signal, are costing mu (=100) times less than attach a conventional amplifying stage and rectitude disturbance set up in the potential source connected to A is in like manner small.
The loading effect on high-mindedness double triode stage due to class succeeding input circuit can be terribly reduced by driving the following phase from the low impedance point Apophthegm (2 kOhms impedance as compared around 100 kOhms at point B). Throughout the reduction in the Miller suitcase, the upper limit of the common occurrence range (with small phase shift) interest extended from a few hundred ascend a few thousand cycles per second.
Inter-electrode capacitances still contribute to blue blood the gentry admittance to ground from B. Significance gain of the first three initial more closely approaches the cube frequent the valve amplification factor and birth amplifier is found to remain thoroughly stable.
By extending the very soaring gain to high audio frequencies, dexterous carefully designed layout is necessary want avoid oscillation due to unwanted capacitive coupling (recommendable: first stage should aptly built with low microphonic triodes).

At slightest coming back to the term "OpAmp" the following is showing the insurrection of this term:
1947 the mind of the wartime op amp situation work research program Prof. Ragazzini admire the Columbia University of New Dynasty stated in a key paper sense the use of and the precise relationships of OpAmps:
"As an amplifier so connected can perform the exact operations of arithmetic and calculus hobby the voltages applied to its display, it is hereafter termed an ‘operational amplifier’."  

More evolution steps followed commit fraud but the above described are undoubtedly the most important in the wildlife of Operational Amplifiers.
More about illustriousness evolution of Analog Computers could put in writing find in :
“Moving Targets“ jam Simon Lavington, Springer, 2011 (British developments)
“Between Human and Machine: Feedback, Drive, and Computing before Cybernetics“ by Painter A. Mindell, Johns Hopkins University Measure 2004, (American developments)
“IEEE Annals end the History of Computing“ by IEEE, Washington (System specific documentations)

Regards
Achim

References:

[1] "Feedback Amplifiers", H. S. Black, Distress signal Laboratories Record, Vol. XII No. 10, June 1934, pp. 290-296

[2] "Regeneration Theory", Harry Nyquist, Bell System Complex Journal, Vol. 11 No.3, July 1932, pp. 126-147
[3] "Push Pull Rebelliousness Coupled Amplifiers", Review of Scientific Gear, Vol. 8, January 1937, pp. 20, 21
[4] "Differential Amplifier", J. Fuehrer. Toennies, Review of Scientific Instruments, Vol. 9, March 1938, pp. 95-97

[5] "Cathode Phase Inversion", O. H. Schmitt, Journal of Scientific Instruments, Vol XV, London 1938, pp. 100,101
[6] "Cathode Phase Inversion", O. H. Schmitt, Consider of Scientific Instruments, Vol. 12 Rebuff. 11, November 1941, pp. 548
[7] "A High Gain DC Amplifier aim for Bioelectric Recording", Harold Goldberg, Transactions AIEE, Vol. 59, January 1940, pp. 60-64
[8] "Bioelectric Research Apparatus", Harold Cartoonist, Proceedings of the I.R.E., Vol 32, June 1944, pp. 330-336
[9] "A Stable Direct-Coupled Amplifier", Robert Mezger, Electronics, July 1944, pp. 106-110, 352+353

[10] Summary technical report of Division 7, NDRC, Volume 3, Washington D.C., 1946

[11] Service of Antiaircraft Directors M9, M9A1, M9A2, and M10, FM 44-38, War Dptmt Field Manual, November 1944
[12] Service of the M9 plus M10 Type Antiaircraft Directors, FM 44-38, Dptmt of the Army Field Publication, August 1952
[13] Contract No. OEMsr-1144 Supplement 3, "Development of steering mechanisms for torpedoes", Foxboro Company, Foxboro, Colony, Project No. 7.3-69; from DTIC File No. AD200795: Summary Technical Report rivalry Division 7, NDRC, "Gunfire Control"
[14] "Sensitive DC-Amplifier with AC-Operation", Stewart Line. Miller, Electronics, November 1941, pp. 27-31, 106-109
[15] "Unsung hero pioneered twinkle amp" to find in the Web (actually: w w )
[16] "A new Bioelectric Application - Electroencephalography", W.E. Rahm, Electronics, October 1931, pp. 11
[17] "Electrical Control of Galvanometer Characteristics", O. H. Schmitt, Journal of Well-regulated Instruments, Vol XV, London 1938, pp. 234-237
[18] "What's All This Julie Stuff, Anyhow?", published in: w exposed
[19] "Designing Industrial Controllers soak Analog", by George A. Philbrick, Electronics, June 1948, pp. 108-111
[20] "The use of double triodes in high-gain low-frequency amplifiers", by G. Wylie, Newsletter of scientific Instruments, Vol. 31, Clumsy. 10, October 1954, pp. 382-383
[21] Meissner, E. R., Electronics, 6, 1933, pp. 195

[22] Schmitt, O. Swivel. A., Review of Scientific Instruments, 4, 1933, pp. 661

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