SDG #040 Linear Power Supply Design - FY3224S FY3200S Sig Gen

The Feeltech FY3200S family, including the 24 MHz FY3224S, is one of the cheapest routes into a two channel DDS function generator, but the bundled switch mode wall adapter is a weak point. Switching noise finds its way onto the output rails, and on a piece of test gear that noise directly limits how clean a low amplitude signal you can trust. This build tackles that problem at the source by replacing the external brick with a purpose designed linear supply.

The design work covers the parts that matter in practice rather than just picking a regulator from a datasheet: choosing a transformer with enough headroom for the generator’s current draw, sizing reservoir capacitance so ripple stays within the regulator’s dropout window, and working out realistic power dissipation so the regulators and heatsinking are not running on the edge. Because the FY3200S needs more than a single rail, the supply has to produce multiple outputs, which is where thermal budget and transformer secondary arrangement start to interact.

The useful takeaway for anyone who owns one of these generators is that the instrument itself is reasonable value, and the supply is the easiest single upgrade to make it behave better on the bench. A linear supply removes the high frequency hash that a switcher injects, and it also gives an opportunity to build the whole thing into a tidier package. It is worth noting the tradeoffs honestly: a linear design is heavier, less efficient, and runs warmer than the brick it replaces, so it suits a permanently installed bench instrument rather than something you carry around. Full schematics are published alongside the video for anyone wanting to replicate the build.