Abstract. This paper presents a new realization of a firstorder current-mode (CM) all-pass filter (APF) using the recently proposed modern active building block (ABB),,namely the current differencing transconductance amplifier (CDTA). The CM APF is made using minimum number of components, namely a single CDTA and one grounded capacitor. The circuit does not use any external resistors and offers the advantages of current-tunable pole frequency, low input impedance and high output impedance. Non-ideal analysis and sensitivity analysis are provided and PSPICE simulation results are included to verify the workability of the circuit