Harmonic Distortion Analysis of CommonSource/Drain Active Balun Circuit

A balun (balanced-unbalanced) circuit converts signals that are single-ended or unbalanced with respect to ground into signals that are differential or balanced with respect to ground, and/or vice versa. An ideal balun generates a pair of differential output signals of balanced amplitudes (0 dB gain difference) and phases (180° phase difference) from a single-ended input signal source. Baluns can be classified as either active or passive baluns depending on the devices used. Active baluns, although unidirectional and more complex to implement, are preferred over their passive counterparts because they can produce gain, occupy less chip area, and can operate at higher frequencies [1-2]. One of the active balun topologies is the common-source/drain active balun circuit shown in Fig.