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 equipment that noise directly limits how clean a low amplitude signal can be trusted to be. This build addresses the problem at the source by replacing the external adaptor with a purpose designed linear supply.

The design work covers the parts that matter in practice rather than simply choosing a regulator from a datasheet: selecting a transformer with enough headroom for the generator’s current draw, sizing reservoir capacitance so that ripple stays within the regulator’s dropout window, and working out realistic power dissipation so that the regulators and heatsinking are not operating at their limits. 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 conclusion 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 noise that a switcher injects, and it also provides an opportunity to build the whole arrangement into a tidier package. The trade-offs deserve honest acknowledgement: a linear design is heavier, less efficient, and runs warmer than the adaptor it replaces, so it suits a permanently installed bench instrument rather than one that is carried around. Full schematics are published alongside the video for anyone wanting to replicate the build.