A High-SNR and Process-insensitive CMOS Capacitive Transimpedance Amplifier with Finely Tunable Conversion Gain

Abstract

A high signal-to-noise ratio CMOS capacitive transimpedance amplifier (CTIA) is proposed for highly sensitive sensor and readout circuits. The presented capacitive-ladder feedback network reduces the equivalent feedback capacitance value required for the low-noise and high-gain CTIA. The very low feedback capacitance realized by a proposed combination of large capacitors allows the conversion gain to be finely tunable, and this also results in a high accuracy that is insensitive to process variations. A prototype 5 V-supply CTIA circuit fabricated with a 0.5-mu m CMOS process has an equivalent noise charge (ENC) of 31 e(RMS)(-) with an input capacitance of 150 pF, and it shows a 36% improvement in the process-insensitivity compared to the conventional CTIA under the same conversion gain.