A Widely-Tunable and Ultra-Low-Power MOSFET-C Filter Operating in Subthreshold

A very wide tuning range ultra-low-power MOSFET-C filter is presented. The wide tuning range in this filter has been achieved without using any switchable components or programmable building blocks, and the cutoff frequency of the filter can be adjusted simply through a controlling bias current. The filter has low-pass characteristics with $f_{c}$ = 20Hz to 184kHz while exhibiting a constant power consumption per cutoff frequency over its entire tuning range that is almost four decades wide. The proposed MOSFET-C filter uses PMOS transistors in subthreshold regime for implementing floating and widely adjustable resistors. The ultra high resistivity of the PMOS devices makes them very suitable for implementing very low frequency and compact filters. Realized in 0.18$\mu$m CMOS technology, the filter exhibits a relatively constant noise and linearity performance over its entire tuning range. The active area of the proposed MOSFET-C filter is 0.09mm$^2$

Design of Highly linear Gm-C Low Pass and Complex Band Pass Filter for High Frequency Application

The present work deals with the design of low pass filters such as 3rd order Gm-C filter, a duty cycle controlled low pass and a complex band pass filter that can be operated for high frequency applications. The linearity and power consumption of a CMOS Gm-C filter are studied and optimized. Firstly, a doubly terminated 3rd order low-pass Gm-C filter is designed

An Optoelectronic Stimulator for Retinal Prosthesis

Retinal prostheses require the presence of viable population of cells in the inner retina. Evaluations of retina with Age-Related Macular Degeneration (AMD) and Retinitis Pigmentosa (RP) have shown a large number of cells remain in the inner retina compared with the outer retina. Therefore, vision loss caused by AMD and RP is potentially treatable with retinal prostheses. Photostimulation based retinal prostheses have shown many advantages compared with retinal implants. In contrary to electrode based stimulation, light does not require mechanical contact. Therefore, the system can be completely external and not does have the power and degradation problems of implanted devices. In addition, the stimulating point is flexible and does not require a prior decision on the stimulation location. Furthermore, a beam of light can be projected on tissue with both temporal and spatial precision. This thesis aims at fi nding a feasible solution to such a system. Firstly, a prototype of an optoelectronic stimulator was proposed and implemented by using the Xilinx Virtex-4 FPGA evaluation board. The platform was used to demonstrate the possibility of photostimulation of the photosensitized neurons. Meanwhile, with the aim of developing a portable retinal prosthesis, a system on chip (SoC) architecture was proposed and a wide tuning range sinusoidal voltage-controlled oscillator (VCO) which is the pivotal component of the system was designed. The VCO is based on a new designed Complementary Metal Oxide Semiconductor (CMOS) Operational Transconductance Ampli er (OTA) which achieves a good linearity over a wide tuning range. Both the OTA and the VCO were fabricated in the AMS 0.35 µm CMOS process. Finally a 9X9 CMOS image sensor with spiking pixels was designed. Each pixel acts as an independent oscillator whose frequency is controlled by the incident light intensity. The sensor was fabricated in the AMS 0.35 µm CMOS Opto Process. Experimental validation and measured results are provided