Ultrawide range square wave impedance analysis circuit with ultra-slow ring-oscillator using gate-induced drain-leakage current

This paper presents area efficient and ultrawide range square wave impedance analysis circuit for biomedical applications. By using a gate-induced drain-leakage current (GIDL), we designed an ultralow current generation circuit which is a key component of the impedance measurement circuit and a GIDL-controlled oscillator operating at ultralow frequency. In addition, the area of the impedance measurement circuit becomes remarkably small due to square waveform current. All impedance measurement circuits are fabricated with a 0.18μm 1P6M standard CMOS technology and occupy 0.43mm2. As results, the proposed GIDL-controlled oscillator circuit successfully oscillated at ultralow frequency of 3.1Hz, and the impedance measurement circuit completely outputs square waveforms with a current amplitude of 50pA. The proposed circuit can measure impedance ranges from 100Ω to 100MΩ.