In this study, in order to demonstrate the versatility of the active building block so-called current differencing transconductance amplifier (CDTA), a current-mode (CM) frequency-agile filter (FAF) application circuit is designed. The derived 2nd-order class 1 CM FAF employs three CDTAs, two capacitors and a single resistor. A layout is designed for CDTA and post-layout simulations are performed using CADENCE Spectre tool with TSMC 0.18 mu m level-49 CMOS technology process and BSIM3v3 parameters. The simulation results confirm theoretical findings.