Tobi Delbruck

Bump Circuits

"Bump" circuits compute similarity and dissimilarity measures between analog voltages. I invented the bump circuit in Mead's lab around 1990 while working on vision chips that measure image blur in order to autofocus. The following paper describes everything I knew at that time:

T. Delbrück. (1991). “Bump” circuits for computing similarity and dissimilarity of analog voltages. Proceedings of International Joint Conference on Neural Networks, July 8-12, 1991, Seattle Washington, pp I-475-479. (Extended version as Caltech Computation and Neural Systems Memo Number 10.)

For more recent information and data about common-mode behavior see the following short paper. This information could be important if you use the antibump circuit as a means for measuring dissimilarity.

T. Delbrück. (2000). Silicon retina for autofocus, Invited session on Bio-inspired Microelectronics, ISCAS 2000, May 27–31, 2000, Geneva, Switzerland, pp. IV-393–396.

These circuits are covered by patents assigned to Caltech.

Synopsis

The simplest bump variety is the bump-antibump circuit

It produces three output currents as a function of the differential input voltage:

Tobi Delbruck

September 13, 2007