Sunday, August 10, 2025

VFD Filament Driver Circuit


Don't give up! I spent the last 3 years troubleshooting this circuit with an LM4871 chip with the goal of supplying a low voltage alternating square wave current across the filament of vacuum fluorescent displays. Spoiler alert: it was the addition of a single 10Ω resistor to lower the voltage from ~5V down to ~3.3V.