In this study, a novel first-order current-mode active-C all-pass filter based on a companding idea is proposed. In the design of the filter, a state space method is used. The proposed structure consists of only two plus-type differential difference current conveyors, nine external MOSFETs, and a single grounded capacitor. The dominant advantages of the proposed filter are briefly described as follows: offering resistorless design, consuming low power, having an electronic tunability property of its pole frequency, and not suffering from the disadvantage of any passive component matching conditions. By cascading two all-pass filters in a closed negative feedback loop, a high-Q band-pass network is designed as an application example. Several simulations including frequency domain and time domain analyses by using the PSpice program are carried out to confirm the theoretical design. All the obtained simulation results are given and discussed.