Two circular electrical aerosol classifiers (CirEACs), i.e., one in large diameters (large version, LV) and the other in small diameters (small version, SV), were designed and their performance was evaluated in this study. The design of CirEACs stems from the demand to have an extended particle size classification range for a miniature electrical mobility classifier while keeping it compact in the package. A CirEAC is constructed by two coaxially aligned cylinders. The particle classification channel is established in the annular spacing defined by two cylinders. Aerosol stream flows into the classification channel via a one-end-closed tube with a series of side holes for reducing the particle loss and keeping particles away from both channel sidewalls. Clean sheath flow is distributed to the entire width of CirEAC channel via a tube similar in design to the aerosol inlet one. The total flow exits the CirEAC from a tube in the same type as the aerosol inlet one. The effects of total flow rate, aerosol-to-sheath flow rate ratio, and particle size on the penetration curves of CirEACs were studied. It is found that the optimal performance of CirEACs was observed when operated at the total flow rate of 1.8 lpm and the aerosol-to-sheath flow rate ratio of 0.2. A 2-D model is also presented to derive the transfer function of CirEACs. The experimental transfer function of CirEAC LV agrees well with that estimated theoretically using the working sheath flow rate (defined as the portion of total sheath flow rate underneath the aerosol slit opening). In comparison, the CirEAC LV possesses a steeper penetration curve, wider total flow rate range (1.2 -3.6 lpm), and broader particle size range (5 - 300 nm) than the CirEAC SV. The CirEAC SV however has a higher transmission efficiency than the CirEAC LV because of its shorter particle classification length.