TIA Linearity Analysis for Current Mode Receivers

Current-mode signal processing offers superior linearity and flexibility in front-end implementation. The linearity of a low-input-impedance Trans-Impedance Amplifier (TIA), which is used as a buffer stage that follows a passive mixer, is important in determining the overall receiver performance. In this paper, the analysis for optimizing the linearity of the feedback TIA is presented. The results helps to estimate the minimum required amplifier gain for a targeted linearity. The accuracy of the analysis is validated by simulating different TIA parameters

A 15 mu W 5.5 kS/s Resistive Sensor Readout Circuit with 7.6 ENOB

A low power SAR logic-based resistive sensor readout circuit is proposed. A high sensitivity thermistor is used for local temperature measurements. The need for a low-noise front-end voltage amplifier is avoided by employing time-domain operation. In each operation step the sensor resistance is compared with the value of a reference resistive DAC which is implemented on chip. Therefore no stable, temperature compensated reference voltage is needed for operation. Furthermore the chip is operational with supply voltages ranging from 1.2 to 1.8 volts. Detailed analyses of the circuit gain and noise are provided. In addition, the effect of circuit topology on the noise performance is discussed. The effect of noise on accuracy of the circuit is also negligible due to resetting the charge-integrating capacitor after each comparison. A prototype chip is fabricated in 0.18-mu m CMOS. The circuit dissipates 15 mu W with 5.5 kS/s conversion rate from a 1.5 V supply. The complete interface circuit has 14 pJ/c-s figure of merit and 7.6 effective number of bits

A Remotely Powered Implantable IC for Recording Mouse Local Temperature with +/- 0.09 degrees C Accuracy

Multiple techniques are presented to implement an ultra-low-power remotely powered implantable system. The temperature is monitored locally by a thermistor-type sensor. The resistive response of the sensor is amplified and resolved in the time-domain. The data is transmitted using a duty cycled free running oscillator operating at 868 MHz. In addition, the sensor interface and data transmitter are time interleaved to improve power link sensitivity. A prototype chip is fabricated in 0.18 mu m CMOS. The implant is powered with a 13.56 MHz inductive link and operates with a minimum power of 53 mu W. The system is capable of recording temperature with accuracy of +/- 0.09 degrees C when 8 times oversampling is done at the base station

A Remotely Powered Implantable Biomedical System With Location Detector

An universal remote powering and communication system is presented for the implantable medical devices. The system be interfaced with different sensors or actuators. A mobile external unit controls the operation of the implantable chip and reads the sensor's data. A locator system is proposed to align the mobile unit with the implant unit for the efficient magnetic power transfer. The location of the implant is detected with 6 mm resolution from the rectified voltage level at the implanted side. The rectified voltage level is fedback to the mobile unit to adjust the magnetic field strength and maximize the efficiency of the remote powering system. The sensor's data are transmitted by using a free running oscillator modulated with on-off key scheme. To tolerate large data carrier drifts, a custom designed receiver is implemented for the mobile unit. The circuits have been fabricated in 0.18 um CMOS technology. The remote powering link is optimized to deliver power at 13.56 MHz. On chip voltage regulator creates 1.8 V from a 0.9 V reference voltage to supply the sensor/actuator blocks. The implantable chip dissipates 595 mu W and requires 1.48 V for start up

Short range remote powering of implanted electronics for freely moving animals

An implantable system for monitoring vital parameters via bio-sensors inside freely moving laboratory animals and its powering system are presented. The required 2 mW are harvested by the magnetic coupling with an external coil placed under the living space of the animal. The servo X-Y rails move the external coil and track the animal. Dynamic power-adaptation keeps the harvested power level constant against misalignments of transmitting coil and moving animal. Entire system and basic blocks integrated using a 0.18 um CMOS technology are presented. Experimental results show the effectiveness of the powering system