These boards allow you to easily build many types of active filters of up to eighth order and test your own filter design.
They are based on Sallen-Key topology, configurable as low-pass and high-pass filter, and Bainter topology for bandstop (notch) filters.
PCBs are designed for single, dual and quad opamps in various packages.
The goal of this project was to design a split power supply powered by single Li-Ion cell.
Power supply is built around TI's TPS65130 which is a boost converter/inverter with wide output voltages range. Naturally high output ripple of switching converter can be reduced by a linear voltage regulator TPS7A3901 (i didn't use it yet, just bypassed it). Output voltage of boost converter can be adjusted by feedback resistors. PCB is designed as breakable and is composed of two parts. First part contains battery holder, USB connector and charger (MCP73831) and LED indicator of battery state and charging state (this part of circuit is completely messed up and is not working as it should). PCB can be split and used as two separate boards. Converter board is designed to fit into a breadboard. Cicuit design of the converter is essentially the typical application schematic from datasheet. This is not a nice-looking or high performance design but it may serve as an inspiration.