This paper presents a new complementary metal-oxide-semiconductor (CMOS) differential voltage-to-frequency converter (VFC) suitable for sensor signal conditioning. Designed in a low-cost 0.18- μm CMOS process, the proposed VFC consumes less than 0.4 mW at a 1.8-V supply. For a differential input range of 0-1.2 V, output frequency varies from 0.1 to 1.1 MHz with a linearity error of less than 0.4%. A new temperature compensation technique keeps the gain error below 2.4% over the whole frequency span for a range of -20°C- +120°C.

This paper proposes a battery-compatible electronic interface based on a general purpose lock-in amplifier (LIA) capable of recovering input signals up to the MHz range. The core is a novel ASIC fabricated in 1.8 V 0.18 µm CMOS technology, which contains a dual-phase analog lock-in amplifier consisting of carefully designed building blocks to allow configurability over a wide frequency range while maintaining low power consumption. It operates using square input signals. Hence, for battery-operated microcontrolled systems, where square reference and exciting signals can be generated by the embedded microcontroller, the system benefits from intrinsic advantages such as simplicity, versatility and reduction in power and size. Experimental results confirm the signal recovery capability with signal-to-noise power ratios down to −39 dB with relative errors below 0.07% up to 1 MHz. Furthermore, the system has been successfully tested measuring the response of a microcantilever-based resonant sensor, achieving similar results with better power-bandwidth trade-off compared to other LIAs based on commercial off-the-shelf (COTS) components and commercial LIA equipment.

A squaring circuit is introduced that boosts the tail current source of an opamp to improve its slew rate. It operates as a differential voltage magnitude detector, which generates opamp tail currents proportional to the magnitude (square) of the opamp's differential input voltage. Experimental results from a fabricated test chip verify current and slew rate enhancement between 900 and 1400% with respect to its initial value with <20% static current increase.

This paper presents a new CMOS differential voltage-to-frequency converter (VFC) which targets front-end sensor interfacing in wireless sensor network applications. The proposed VFC, designed in a low-cost 0.18 μm CMOS technology supplied at 1.8 V, shows 0–1 MHz output frequency for 0–1.2 V differential input operation with nonlinearity error less than 0.4% and power consumption less than 0.4 mW. A temperature compensation technique keeps the error below 5.3% over all the frequency range for a (−20 ^∘C,+120 ^∘C) span.