Transistor Cascode Topology
What is the earliest reference to a cascode topology using
The cascode topology was invented to solve the Miller effect  in
triode amplifiers. However, with the invention of the pentode (at
right), with its screen and suppressor grids, the cascode was no longer
necessary and was "forgotten." After the invention of the transistor
in 1947, the cascode amplifier had to be "re-invented" to solve the
Miller effect in common-emitter transistor amplifiers.
At least, that's the story I've always heard. As the Italians say,
Se non è vero, è ben trovato (Even if it's not
true, it makes a good story).
Jim Williams ran a contest  and was subsequently pointed to  the
earliest use of the word "cascode" in a paper by Hunt and Hickman
. But what is the earliest reference to a cascode topology using
Please note that we are not looking for the first transistor stack, or
for the first common-emitter common-base amplifier cascade. We're
looking for the first transistor stack with the word "cascode" referring
to it. If you have any leads or references, please contact
Kent Lundberg (I'm also
interested in references that retell the myth).
- Gray and Searle (1969, reference ) discuss a transistor cascode
amplifier without comment or reference, or any discussion of the
etymology of the name.
- Thornton et al (1966, reference ) show a cascode along with the
caption "A common-emitter amplifier driving a common-base stage, similar
to the vacuum tude "cascode" circuit. It avoids the loading effect of
C_mu on the input and is capable of large voltage swings at the
- Jim Williams suggested the Tektronix 1A7 plug-in manual (copyright
1965) as a possible "first use." Page 3-4 shows the following topology
with the note "V124, V134 and Q144 operate as a cascode amplifier."
However I'm going to disallow this reference, since V124 and V134 are
vacuum tubes (nuvistors).
- Update December 2006: Our correspondent Dennis
Cushing has reported the earliest reference found so far, a paper from
January 1960 titled "Analysis of the transistor cascode configuration"
. This paper also includes an acknowledgement: "It is believed that
the transistorized cascode circuit was first used by S. H. Bowers of
S.R.D.E., Christchurch." S.R.D.E. is the British Signal Research and Development
Unfortunately, the myth of the forgotten art of the cascode is
demonstratably false. As late as 1956, books such as Arguimbau and
Alder  and Stewart  discuss vacuum-tube cascodes (but not
Arguimbau and Alder show the the following circuit along with the
caption "6BQ7-A cascode":
Stewart says, "The cascode amplifier is important because it has small
circuit noise and a reasonably high gain... It consists of two tubes
which may be either triodes or pentodes, with triodes best for low
noise" (pages 363-364). Stewart also claims "In recent years the
cascode amplifier has gained fame even to the layman as the input stage
of television receivers (following the antenna), although it originally
was developed as the input stage of radar intermediate-frequency
amplifiers" (page 365). Stewart appears to be talking about reference
, but that work is clearly predated by Hunt and Hickman .
These quotes seem to refute the "forgotten art" myth pretty well.
- John M. Miller. Dependence of the input impedance of a
three-electrode vacuum tube upon the load in the plate circuit.
Scientific Papers of the Bureau of Standards,
vol. 15, no. 351, pages 367-385, 1920.
- Jim Williams, "A Monolithic Switching Regulator with 100mV Output
Noise," Linear Technology Corporation, Application Note 70, October
1997 (footnote 14).
- Jim Williams, "Circuitry for Signal Conditioning and Power
Conversion," Linear Technology Corporation, Application Note 75,
March 1999 (footnote 12).
- F.V. Hunt and R.W. Hickman, "On Electronic Voltage Stabilizers,"
Review of Scientific Instruments, January 1939, pp. 6-21
- Paul E. Gray and Campbell L. Searle. Electronic Principles:
Physics, Models, and Circuits. Wiley, New York, 1969, pages
- Richard D. Thornton, J.G. Linvill, E.R. Chenette, H.L. Ablin,
J.N. Harris, A.R. Boothroyd, J. Willis, and Campbell L. Searle.
Handbook of Basic Transistor Circuits and Measurements,
volume 7 of Semiconductor Electronics Education Committee
Series. Wiley, New York, 1966, pages 12-13.
- Lawrence B. Arguimbau and Richard B. Alder. Vacuum-Tube
Circuits and Transistors. Wiley, New York, 1956, page 91.
- John L. Stewart. Circuit Theory and Design. Wiley, New
York, 1956, pages 363-365.
- George E. Valley, Jr. and Henry Wallman. Vacuum Tube
Amplifiers, volume 18 of MIT Radiation Laboratory
Series. McGraw-Hill, New York, 1948, page 440.
- J.R. James, "Analysis of the transistor cascode configuration,"
Electronic Engineering, pages 44-48, January 1960.
Kent H Lundberg.
January 5, 2007.