In this paper, we propose a universal biquad filter that can realize all types of 2nd-order functions, such as Low-pass Filters (LPF), High-Pass Filters (HPF), Band-Pass Filters (BPF), Band-Elimination Filters (BEF), and All-Pass Filters (APF). Also, the filter types can be programmable digitally with built-in switches. The proposed circuit can be realized by using a CMOS technology that is suitable for a mixed digital-analog LSI. In addition, the circuit can operate in high frequencies with a low power supply voltage because it is based on a current-mode circuit. Finally, the proposed circuit is simulated by PSpice to confirm its characteristics.