Abstract: Systems, methods, and other embodiments associated with radio frequency identification (RFID) circuits are described. According to one embodiment, a radio frequency identification circuit includes an antenna network, including an antenna and an antenna interface coupled to the antenna, wherein the antenna interface includes first and second capacitors, which are coupled in series with the antenna. An integrated circuit includes a first pin and a second pin coupled respectively to a first node and a second node of the second capacitor and configured to operate as a reader and a tag in combination with the antenna network, and an amplifier embedded in the integrated circuit and configured to provide an output admittance determined by a ratio of current and voltage negative feedback signals such that a frequency response of the combined integrated circuit and antenna network is adjustable without increasing power consumption of the RFID when operating as a reader.