Lossless CMOS active reciprocal two-port inductor and application in a series LC filter

A differential active reciprocal two-port inductor with a high quality factor is presented. In the transconductor design, a cross coupled pMOS transistor pair is utilized to serve as active load to generate negative output admittance. With an additional compensation resistor, lossless active inductors can be realized. A 24.7 nH active two-port inductor is designed having a simulated series resistance of -1 Ω. To demonstrate the concept, the proposed active two-port inductor is used in a series LC tank, which acts as a first order bandpass filter. The bandpass filter is fabricated in a standard 0.13 μm CMOS process. The measured filter exhibits 0.26 dB gain and 17 dB return loss at the center frequency of 2.45 GHz. A common mode suppression of 27 dB is also achieved. The series inductance and resistance are extracted as 22.24 nH and -5 Ω. The proposed active two-port inductor consumes 2.5 mA at 1.2 V and occupies an area of 150×50 μm².