Jim Williams and Electronic Music
Analog circuit guru Jim Williams passed away on June 12, 2011. While
he never expressed a personal interest in electronic music, he did
write several interesting application notes for National Semiconductor
Corp that are relevant to electronic music (even if NSC didn't credit
him on the app notes).
For more information about the application notes that he wrote for National Semiconductor, see this research bibliography or the complete bibliography.
- App Note 262, Applying dual and quad FET op amps (which includes a "Voltage controlled sine wave oscillator" on page 4)
- App Note 263, Sine wave generation techniques
- App Note 286, Applications of the LM392 comparator op amp IC (which includes the often-cited "Exponential V/F converter for electronic music" on page 4)
- App Note 294, Special sample and hold techniques
- App Note 299, Audio applications of linear integrated circuits
- App Note 311, Theory and applications of logarithmic amplifiers
Also, Jim wrote many, many app notes for Linear Technology, including
Note 14, Designs for high-performance voltage-to-frequency
converters, which includes "e^x transfer function V-to-F
converter" on page AN14-14. For more information about the sitxy-two app
notes he wrote for Linear Technology, see the blog
Reading Jim Williams.
Footnote: Of course, I am not the first person to realize Jim's
authorship of these app notes. In fact, I found the following quote on
page 12 of Barry Klein's 1995 update booklet to his book (Barry
Klein, Electronic Music Circuits, Indianapolis: Sams & Co.,
1982) where he discusses discrete voltage-controlled-oscillator
circuits. The two application notes that he lists are National
Semiconductor AN-299 "Audio Applications of Linear Integrated
Circuits" and Linear Technology Application Note 14 "Designs for High
Performance Voltage-to-Frequency Converters".
AN-299 Audio Applications of Linear Integrated Circuits
I want to publicize these facts, so that Jim gets the credit he deserves.
LT1055 Data Sheet/Application Note 14
Jim Williams of Linear Technology wrote both of these application
notes. I wrote him about them and he gave me a little background on
them. The AN-299 VCO utilizes the CA3046 transistor array. He stated
that even if the exponential transistor was ideal the performance
would be degraded by the ramp reset time. His second circuit in
LT1055/AN14 notes utilizes a charge pump IC -- the LT1043 -- to
eliminate the dead time errors. He thinks this circuit has about a 2X
improvement in exponential performance...
Written August 2011 by Kent
Updated January 2012.