A 2-Vpp Linear Input-Range Fully Balanced CMOS Transconductor and Its Application to a 2.5-V 2.5-MHz Gm-C LPF

Tetsuro ITAKURA  Takashi UENO  Hiroshi TANIMOTO  Tadashi ARAI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E83-A   No.11   pp.2295-2302
Publication Date: 2000/11/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: Analog Signal Processing
analog signal processing,  integrated electronics,  fully balanced CMOS transconductor,  common-mode rejection ratio,  

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A fully balanced (FB) transconductor using two multi-input single-ended (SE) CMOS transconductors is proposed, where the transconductors use MOS transitors operating in a triode region for achieving a wide linear input-range. SE circuits are easier to design than differential circuits and inherently reject common-mode (CM) signals. The multi-input structure is used to make a CM 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 transconductor achieves a 2-Vpp linear input range at a 2.5-V power supply and consumes 1.74 mA. The output resistance of the FB transconductor is 2 MΩ. It operates at 2 V with a linear input-range of 1.2 Vpp and at 1.6 V with a linear input-range of 0.9 Vpp. 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.