This paper presents a simple 1.2 V low-power rail-to-rail class AB operational amplifier (OpAmp) suitable for integrated lock-in amplifiers. The proposed OpAmp has been designed in a standard 0.18 μm CMOS technology. For a 1.2 V single supply and 68.6 μW power consumption, simulations shows a 81 dB open loop gain, 64° phase margin, 13 MHz unity gain frequency for a capacitive load of 10pF and 75 dB CMRR. Adaptive biasing provides 30.7 V/μs slew-rate for a 10 pF load. A compact and reliable lock-in amplifier (LIA) has been designed using the proposed circuit. The designed LIA has a power consumption of 135 μW and recovers signals up to 1 MHz with relative errors below 2.6 % for noise and interference signals of the same amplitude as the signal of interest.
The increasing application of sensor networks in many different fields causes a growing demand of low-cost passive
sensors for monitoring physical variables as temperature, pressure or ambient humidity. These sensors need a
conditioning circuit that allows an easy interface to a microcontroller, taking advantage of the full range of the sensor
and reducing the microcontroller requirements. This paper presents a conditioning electronics designed to transform the
output of low-cost resistive sensors to a frequency variable signal. The circuit is designed to use the full frequency range
available, providing a good resolution. These quasi-digital signals are compatible to the logic levels of a standard low-power
microcontroller, allowing its connection through a digital I/O port.
This paper presents a study of mismatch effects in a digitally programmable analogue processor designed for small embedded applications. Circuit programmability allows for its adaptation to deviations in circuit operation or environmental effects. Starting from circuit simulation data, the system-level operation is modeled, showing its robustness to circuit mismatch. Simulation results of the proposed processor applied to compensate the response of a sinusoidal sensor and its robustness to mismatch are presented.