In this paper, a wireless telemetry using the near-field coupling technique with round-wire coils for an implanted pacemaker is presented. The proposed system possesses an external powering amplifier and an internal bidirectional microstimulator. Even with a low induced voltage, all the circuitries associated with the implantable stimulator are operated normally by the coupling power interface, which includes an efficient rectifier, one fully-integrated regulator, and a charge pump. To acquire cardiac signal, a low-voltage and low-power monitoring analog front end (MAFE) performs the functions of immediate threshold detection and data conversion. In addition, pacing circuits, which are responsible for stimulating heart tissue, are employed to overcome the huge voltage difference between the pulse generator (PG) and its digital-to-analog (D/A) controller. The chip is fabricated by TSMC with 0.35 μm CMOS technology to manifest the monitoring and pacing function under inductively powering communication. With a model utilizing lead and heart tissue, a - 5-V pulse at a stimulating frequency of 60 beats per minute (bpm) is delivered while only consuming a power of 31.5 μW.