5/19/16: Fundamentals of Operational Amplifiers

Do we have to worry about aliasing when using chopper-based op amps to build analog filters?

  • In an old-style chopper-stabilized amplifier, it would not work out well as a filter exactly because of aliasing.   In our newer designs, such as the AD8628, which we call zero-drift, they do not work in the same manner as a 'true' chopper.  The input is not ever truly disconnected from the signal path.  There is still a high-frequency noise from sampling an internal signal that relates to the offset, so that is present at the output.   These zero-drift can be used quite well in low-pass filters up to 10-20kHz.  They are primarily intended as amplifiers for low-level sensors and similar applications.