This paper proposes a new symmetric differential-pair structure for the active inductor. The CMOS spiral inductor occupies a large chip size and is difficult to obtain a high Q-factor. A symmetric differential-pair active inductor circuit topology with feedback resistor is proposed, which can substantially improve its equivalent inductance and quality-factor. This feedback resistance differential-pair active inductor was implemented by using 0.18-mum TSMC RF CMOS technology, which demonstrates a maximum quality-factor of 28 with a 27-nH inductance. The proposed active inductor has one hundredth of chip size of a spiral inductor and it also shows more than ten times wide dynamic range and twice higher Q-factor compared to the conventional 1-port active inductor circuits. In addition, this configuration can be easily implemented using the series circuit.