Research Experience

A. Analog and RF Circuit Design for Biomedical Instrumentation

• Optimal MOSFET dimension formulation for a self-cascode structure with capacitive feed-back
• Calculation of oscillation frequency and required transconductance to startup for a self-cascode oscillator structure
• Mathematical formulation of Phase Noise variation with capacitance ratio for a self-cascode oscillator structure
• Development of Low-Voltage Low-Power injection-locked transmitter using back-gate coupling and self-cascode structure
• Simulink implementation of the behavioral model of a back-gate coupled injection-locked oscillator
• Study suitable RF band for wireless medical telemetry
Development of a low-power CMOS read-out circuit with FSK/OOK telemetry option for an inductively powered implant system
• Development of a CMOS read-out circuit for a MEMS-based capacitive pressure sensor with high resolution and high degree of linearity
• Simulink implementation of the behavioral model of the CMOS read-out circuit for MEMS-based capacitive pressure sensor

B. Developed Integrated Circuits (IC)

1. Low-Voltage Low-Power Body-Coupled Injection-Locked Oscillator for Low-Power Injection-Locked Transmitter Applications(2008)

A low-voltage low-power injection-locked oscillator (ILO) has been designed and implemented using 0.18 μm RF CMOS process. Capacitive feedback with self-cascode structure has been used to resemble a Colpitts oscillator structure that helps to provide better oscillator performance. Mixer functionality of body driven MOSFET has also been utilized to achieve injection-locking without increasing power consumption much. Simulation and measurement results indicate that the oscillator can operate with 1 V supply voltage with DC power consumption in the range of 2 mW. The designed circuit also shows an increment of only 11.6 μW of power for 1 dBm increase of injection signal power. In future, the deigned ILO will be utilized to realize a low-power injection-locked transmitter.

2. Design of a low-power current signal processing circuit for MEMS-based capacitive pressure sensor using TSMC 0.35 μm bulk CMOS process (2007)

A CMOS read-out circuit has been implemented in 0.35 μm process for a MEMS based capacitive pressure sensor. The circuit can produce a dc output depending upon the sensor variation. The system manifests two charge amplifiers, two diode rectifiers, two RC filters and one instrumentation amplifier. The circuit has a resolution of 1mV/500aF.

3. Two Stage Operational Transconductance Amplifier (OTA) with Miller Compensation realized in AMI 0.5 μm bulk CMOS process (2007)

A two stage OTA with single ended output has been realized in 0.5 μm process. Miller compensation has been used increase the stability of the OTA. The OTA has been simulated for different temperatures and process corners with different load conditions. The designed OTA has the following performance criteria: Supply voltage 5 volt, total current 250 μA, Gain > 75 dB, GBW >10 MHz, PM 55o, ICMR 0 to 4V, Input offset voltage 300 μV, PSRR+ > 95 dB, PSRR- > 80 dB, SW 6V/µS, CMRR > 83 dB, Input Noise < 20 nV/sqrt(Hz).

4. Bandgap Voltage Reference Circuit using Weak Inversion MOSFET realized in AMI 0.5 μm bulk CMOS process (2007)

The bandgap reference has been formed by using CTAT and PTAT reference. The PTAT reference current is generated by using a MOSFET operating in the weak inversion region. The generated PTAT current is driven into a resistive load and a diode. VREF is in the range of 1.25+11%, Total supply current IT < 30uA, TCVREF < 200ppm/oC.

5. Design of a 915 MHz Injection-Locked oscillator using AMI 0.5 μm bulk CMOS process (2007)

6. Design of a Sensor Signal Read-out Circuit and Telemetry unit using AMI 0.5 μm bulk CMOS process (2006)

7. 915 MHz Low Noise Amplifier (LNA) using AMI 0.5 μm bulk CMOS process (2006)

8. Design of an Analog Counter using AMI 0.5 μm bulk CMOS process (2006)

9. 4-bit Digital Counter using AMI 0.5 μm bulk CMOS process (2006)