TDA2003 is a cheap amplifier that is designed to run on single rail power supplies (unipolar). It provides a high output current capability (up to 3.5A), very low harmonic and cross-over distortion. 18W TDA2003 bridge Circuit Diagram TDA2003 bridge 18W amplifier TDA2003 can be used as an BCL (bridge amplifier) and car deliver up to 18W.