Home » , » Naming the Op Amp

Naming the Op Amp

Further wartime op amp development work was carried out in the labs of Columbia University of New York, and was documented in 1947 by the program’s research head, Professor John Ragazzini (Reference 40: John R. Ragazzini, Robert H. Randall and Frederick A. Russell, "Analysis of Problems in Dynamics by Electronic Circuits," Proceedings of the IRE, vol. 35, May 1947, pp. 444-452. (An overview of operational amplifier uses, and 1st formal definition of the term)). This often-cited key paper is perhaps best known for coining the term operational amplifier, which of course we now shorten to the more simple op amp. Quoting from this paper on the naming:
"As an amplifier so connected can perform the mathematical operations of arithmetic and calculus on the voltages applied to its input, it is hereafter termed an ‘operational amplifier’."
The Ragazzini paper outlines a variety of ways that op amps can be used, along with their defining mathematical relationships. This paper also references the Bell Labs work on what became the M9 gun director, specifically mentioning the op amp circuits used.
The work that gave rise to the above paper was a late WWII NDRC Division 7 contract with Columbia University(Mindell (reference 39, again) lists in his Table 6-1, a contract No.76 for "Fire Control Electronics," with Ragazzini as investigator, running from November 15, 1943 to September 30, 1945, at a cost of $85,000. The Division 7 supervisor for this Columbia University project is listed as SHC, for Samuel H. Caldwell). At that time, Loebe Julie was a bright young research engineer in the Columbia University Labs. Julie did work on these early op amps, which were aimed at improvements to the M9 gun director system, stated contractually as "Fire Control Electronics".
Reportedly working against the wishes of Ragazzini, Julie was engaged to do this work at the behest of analog computer engineer George A. Philbrick, part of the Division 7 team (References 41 and 42: George Rostky, "Unsung Hero Pioneered Op Amp," EE Times, March 24, 1997, or, http://www.eetonline.com/anniversary/designclassics/opamp.html (A narrative on the op amp work of Loebe Julie at Columbia University during WWII [and footnoted in the Ragazzini paper]. A schematic diagram of the Julie op amp is included) and Bob Pease, "What’s All This Julie Stuff, Anyhow?," Electronic Design, May 3, 1999, or, http://www.elecdesign.com/1999/may0399/pease/0503bp.shtml (Another narrative on the op amp work of Loebe Julie at Columbia University during WWII [and footnoted in the Ragazzini paper])). Julie completed a two-tube op amp design, using a pair of 6SL7 dual triodes in a full differential-in/differential-out arrangement (see Reference 41, again). But, for whatever the reason, his lab boss Ragazzini gave Julie's amplifier work but a minor acknowledgment at the very end of the paper.
The op amp schematic shown in the Ragazzini paper (Fig. 1 of Reference 40) doesn’t match the schematic attributed to Julie (Reference 41, again). And, Ragazzini doesn't cite any specifications for this circuit, so the origins and intent aren't clear, unless it was intended as a modest performance example. It doesn't seem as if it could be an M9 system candidate, for a couple of reasons.
For example, briefly analyzing the Fig. 1 Ragazzini op amp, it seems doubtful that this particular design was really intended to operate in the same environment as the original M9 op amp (Reference 30, again, or Fig. 3 above). Swartzel's three-stage circuit used a triode and two pentodes, with one of the latter a power output stage. So, Ragazzini's circuit wouldn't appear to match the gain characteristics of Swartzel's design, as it used three cascaded triodes. It also wouldn't be capable of the same output drive, by virtue of its use of a 6SL7 output stage, loaded with 300kΩ.
Share this article :


Post a Comment

Please wait for approval of your comment .......