A 2-V-pp linear input-range fully balanced CMOS transconductor and its application to a 2.5-V 2.5-MHz Gm-C LPF

A fully balanced (FB) transconductor using two multi-input single-ended (SE ) CMOS transconductors is proposed, where the transconductors use MOS trans itors operating in a triode region for achieving: a wide linear input-range . SE circuits are easier to design than differential circuits and inherentl y reject common-mode (CM) signals. The multi-input structure is used to mak e a Chi feedback loop and to determine an output CM voltage. A high-output- resistance current mirror is used in converting a differential signal to a single-ended signal in order to achieve a high common-mode rejection ratio (CMRR) and a high output-resistance of the transconductor. The FB transcond uctor achieves a 2-V-pp linear input range at a 2.5-V power supply and cons umes 1.74 mA. The output resistance of the FB transconductor is 2 M Omega. It operates at 2 V with a linear input-range of 1.2 V-pp and at 1.6 V with a linear input-range of 0-9 V-pp. A 2.5-V 2.5-MHz FB Gm-C filter using the FB transconductors achieved a CMRR of 45 dB and a passband IIP3 of 32 dBm.