Output Impedance Measurement in Low-Power Sources and Conditioners

The internal output impedance of power sources and power conditioners has a strong impact on conducted interference, particularly in mixed-signal circuits. Further, the transient response of power sources and power conditioners in front of sudden load changes should not involve voltage swings beyond the operating voltage tolerance of the load. We propose a measurement method that is able to determine both the output impedance and the transient response of low-power sources and conditioners by using an operational amplifier (OA)-based dynamic load. Experimental results for some linear voltage regulators, power supplies, and batteries validate the method and demonstrate that it can reliably measure impedance magnitudes as low as 20 mOmega.