A digitally calibrated CMOS transconductor with a 100-MHz bandwidth and 75-dB SFDR

This paper proposes a high-speed CMOS transconductor with its linearity enhanced by current--voltage negative feedback. This voltage-to-current converter is mainly composed of two parts: an operational transconductance amplifier and a pair of feedback resistors. The measured spurious-free dynamic range of the transconductor achieves 72.6 dB when the input frequency is 100 MHz. To compensate for common-mode deviation due to process and temperature variation, digital calibration circuits are added. With the proposed calibration scheme, the common-mode voltage deviation is eliminated within 24 clock cycles. Fabricated in TSMC 0.13-[micro]m CMOS process, the transconductor occupies 220 x 160 [micro][m.sup.2] active area and consumes 6 mW from a 1.2-V supply where the calibration circuits only consume 16% of the overall power consumption. Index Terms--High-linearity amplifier, operational transconductance amplifier (OTA), transconductor, voltage-to-current converter.