Jamel Nebhen

A temperature compensated CMOS ring oscillator for wireless sensing applications

This paper presents a CMOS voltage controlled ring oscillator (VCO) with temperature compensation circuit suitable for low-cost and low-power wireless sensing applications. To operate at low frequency, a control voltage generated by a CMOS bandgap reference (BGR) is described and the measurement results of the fabricated chips are presented. The output voltage of the reference is set by resistive subdivision. In order to achieve small area and low power consumption, n-well resistors are used. This design features a reference voltage of 1V. The chip is fabricated in AMS 0.35 µm CMOS process with an area of 0.032mm2. Operating at 1.25V, the output frequency is within 200±l0kHz over the temperature range of −25°C to 80°C with power consumption of 810µW.

A 250 μW 0.194 nV/rtHz Chopper-Stabilized instrumentation amplifier for MEMS gas sensor

In this paper, a low-noise, low-power and low voltage Chopper Stabilized CMOS Amplifier (CHS-A) is presented and simulated using transistor model parameters of the AMS 0.35 μm CMOS process. Chopping is used to modulate the offset away from the output signal where it can be easily filtered out, providing continuous offset reduction which is insensitive to drift. The CHS was simulated using typical transistor model parameters BSIM 3V3 of the 0.35 μm CMOS process technology from AMS [1]. Under at ±1.25 V power supply and a voltage gain of 49dB, the total power consumption is 250 μW only. At the same simulation condition, it achieves a noise floor of 0.194 nV/√Hz within the frequency range from 1 kHz to 10 kHz and the inband PSRR is above 90, the CMRR exceeds 120 dB. The circuit occupies an effective small chip area of 3.233 mm2.

Low noise CMOS chopper amplifier for MEMS gas sensor

We describe in this paper a low-noise, low-power and low-voltage analog front-end amplifier dedicated to high resistive gas sensor detection. A mobile sensor system for very low level signals such as gas spikes detection is required to implement with a scaled CMOS technology. For a key circuit of these systems, a Chopper Stabilization Amplifier (CHS) which suppresses DC offset and 1/f noise figure of MOS devices is commonly used.

Low-noise CMOS amplifier for readout electronic of resistive NEMS audio sensor

Investigation of readout electronic dedicated to electromechanical audio sensor is presented. The circuit is able of reading piezoresistive gauge implemented with silicon nanowire (NEMS) and bring electromechanical signal to high-resolution digital output. Low-noise low-power CMOS operational transconductance amplifier (OTA) is presented. The low-noise amplifier (LNA) has been designed in a 0.28 μm CMOS process with a 2.5 V supply voltage and occupies an area of 120 × 160 μm2. For the Post-layout Simulation, the OTA achieves a 65 dB DC gain. It achieves a noise floor of 6 nV/√Hz within the frequency range from 1 Hz to 10 kHz. The total power consumption including the common mode feedback circuit (CMFB) and the biasing circuit is 150 μW.

Low-noise CMOS analog-to-digital interface for MEMS resistive microphone

The design and implementation of a CMOS integrated analog to digital interface dedicated to hybrid integration of MEMS resistive microphone is presented. Audio sensing is achieved with an innovative low-cost technology that uses single crystal piezoresistive silicon nanowires as transducer in a MEMS. The circuit composed of a low-noise instrumentation preamplifier followed by a single bit fourth order continuous-time sigma-delta modulator (CT-ΣΔM) includes bias circuit for sensor. To join low power applications where extensive digital processing is employed, 0.28 μm CMOS process with a 2.5 V supply has been adopted. The test chip occupies an area of 1 mm2. Post-layout simulation exhibits promising performances where noise density is below 8 nV/VHz within the frequency range from 10 Hz to 10 kHz. Complete interface circuit features a current consumption of 2.4 mA.

Low-cost auto-calibration of passive polyphase filter in image reject receiver

A low-cost auto-calibration technique of Radio-Frequency (RF) Passive Polyphase Filter (PPF) for high image rejection in low Intermediate Frequency receiver is presented. The resistance values of the filter are process and temperature dependent with great mismatch constraints especially in the RF domain. That can severely impact the circuit performances if not controlled. In order to overcome this limitation, an in-line auto-calibration of the PPF resistance values, based on Design Of Experiment (DOE) methodology, is presented. Using DOE, a model is derived from thermal and process deviations of the chip responses. This approach results in a robust and low-cost solution.