Differential Active Balun Circuit DC Analysis

The differential active balun shown in Fig. 1 is composed of 3 transistors namely M1 and M2 for the differential output, and M3 for the tail current. The input signal is applied at the input of one of the differential pair transistors and will ideally split equally between the pair with same amplitude and 180 degrees phase shift. Interestingly, this active balun topology is capable of producing gain.