Inside a 1980s filter chip that uses switched capacitors
Summary
This article analyzes the MF10 switched-capacitor filter chip from the 1980s, detailing the die structure, 72 capacitor squares, and CMOS switches that implement the switched-capacitor network. It explains how the clock-driven capacitors emulate resistors, the non-overlapping clocking to prevent shorting, and the state-variable filter architecture that yields high-pass, band-pass, and low-pass outputs. The piece combines reverse-engineering insights with historical context on Harris/MF10 hardware and its evolution.