A design of Transimpedance Amplifier using OTA as a feedback resistor for patch-clamp measurement system

Patch-clamp system is commonly used to measure ion current flowing through ion channel on cell membrane. By integration of this system, it is realized high density multi-channel system. In this paper, we designed Transimpedance Amplifier (TIA) in a patch-clamp system for single channel recording. Proposed TIA use OTA (Operational Transconductance Amplifier) as a feedback resistor, the size of TIA is drastically decreased compare to previously designed TIA using poly silicon resistor. The system was fabricated using the 0.18μm CMOS process. The designed size is 200 μm by 70 μm. We confirmed by simulation and measurement that the TIA has enough performance for single channel recording. The value of OTA resistance is variable from 5 MΩ to 500 MΩ by adjusting bias voltage. The bandwidth covers at least 10.3 kHz. Input-referred noise is 0.86 pArms in bandwidth that is extremely small value in on-chip transimpedance amplifiers for patch-clamp method. Power consumption of the TIA is 52.3 μW. Input range is ±50 pA when the value of resistance is 500MΩ.