An active common mode filter is configured to be positioned between a power supply and a switching converter-device/load for reducing common mode noise. The active common mode filter includes an active capacitor that has a sensing stage including one or more sensing capacitors, an amplifying stage including a common collector amplifier for mitigating an input voltage divider effect coupled to a common emitter amplifier for providing high gain, and an injection stage including one or more injection capacitors. Depending on the required attenuation in different applications, a multistage active common mode filter may be formed with a necessary number of stages, each stage including an active capacitor and an inductor.