A new technique for analog multiplication

Describes a new method using emitter current crowding for performing accurate multiplication of analog signals using devices of special geometry but capable of fabrication with a standard bipolar process. A narrow region of current injection-a carrier domain-can be positioned on an emitter by one electrical input and controlled in magnitude by a second input. The resistive epi layer resolves this current into a differential output proportional to the product of the inputs. A key advantage of these multipliers is their low noise. The basic principle can be applied to many other nonlinear operations. A two-quadrant and a four-quadrant multiplier are described.