A Transistor Ladder Voltage-Controlled Filter Implemented on a Field Programmable Analog Array

摘要

Before fast, inexpensive digital electronics became commonplace, analog techniques dominated the field of music synthesis. Over time, much of the art has moved to the digital domain, which allows for greater flexibility than traditional analog systems. Many enthusiasts still argue that the "warmth" of analog systems is difficult to recreate digitally. Recent developments concerning Field-Programmable Analog Arrays may permit the creation of analog synthesizers that enjoy the ease of rapid reconfigurability previously associated only with digital synthesizers, allowing musicians to characterize individual circuit elements and try different topologies. This paper presents an implementation of a particularly famous voltage-controlled filter design, namely, the transistor ladder filter. The original formulation, which was based on BJTs, readily maps to MOSFETs operating in the subthreshold region. The implementation is aided by the use of high-level software design tools in Simulink.