This article covers an extended, symmetrical version of an adjustable DC load. The design is suitable, for example, for testing the typically symmetrical power supplies used in audio power amplifiers.

New Version

The circuit from the previous version is equipped with two identical output stages, each rated for a maximum of 5 A, which can be connected in parallel to double the maximum current. Since the ground of the power supply under test is connected to the grounds of any connected function generator and oscilloscope, testing negative power supplies would cause problems.

In this new version, one of the two output stages was modified so that negative voltage sources can be tested, and with both output stages, even symmetrical power supplies can be tested without potential issues. As before, the power supply under test can be loaded not only statically but also dynamically to determine its control characteristics.

Principle

The new block diagram is shown in Figure 1. ...