This thesis is composed of two parts : a 3¡ÑVDD bidirectional mixed-voltage-tolerant I/O buffer, and a 2¡ÑVDD output buffer with process and temperature compensation. In the first topic, a 3¡ÑVDD bidirectional mixed-voltage-tolerant I/O buffer, which is able to tolerate 3¡ÑVDD using stacking transistors in the output stage, is proposed. These transistors are biased by corresponding voltage levels which are generated by a dynamic gate bias generator and a floating N-well circuit when transmitting or receiving signals. In order to prevent the input stage transistors from gate-oxide overstress, an NMOS clamping technique is used to block high input voltages. This design can receive and transmit 0.9 V to 5.0 V (0.9/1.2/1.8/2.5/3.3/5.0 V) signals, which has been implemented using TSMC 1P6M 0.18 £gm CMOS process. The second topic shows a 2¡ÑVDD output buffer with process and temperature compensation using 1P6M 0.18 £gm CMOS process. In this design, a novel process and temperature variation detector is proposed to detect the corners of NMOS and PMOS, respectively. The driving capability of the output stage is enhanced at those corners with low output currents. By contrast, the driving currents is reduced at those corners with high output currents to reduce the variation of output slew rate.

The thesis is composed of tow topics: a fully bidirectional mixed- voltage-tolerant I/O cell using a new output stage circuit and a sub-3¡ÑVDD wide range fully bidirectional mixed-voltage-tolerant I/O cell. The first topic discloses a mixed-voltage-tolerant I/O cell implemented using 2P4M 0.35 £gm CMOS process, which uses a low static power dynamic gate bias generator providing three different logic voltage levels to the output stage to avoid gate oxide reliability and leakage current. The design also reveals a new output stage circuit, which enhances the output current to resolve the poor driving capability caused by the slow mobility and body effect of the stacked PMOS. The second topic shows a sub-3¡ÑVDD wide range fully bidirectional mixed-voltage-tolerant I/O cell using 1P6M 0.18 £gm CMOS process, which employs a new dynamic gate bias generator and a PAD voltage detector to provide appropriate gate biases. The design includes a new gate tracking circuit and a floating N-well circuit to avoid gate oxide reliability and leakage current, which relaxes the body effect at the output PMOS.

This thesis is composed of two parts: a 3¡ÑVDD mixed-voltage-tolerant I/O buffer with 1¡ÑVDD CMOS standard device, and a PVT detector for 2¡ÑVDD output buffer with slew-rate compensation. In the first topic, a 3¡ÑVDD bidirectional mixed-voltage-tolerant I/O buffer, which has been implemented using a typical TSMC 0.18 £gm CMOS process, is proposed with a Dynamic gate bias voltage generator to provide appropriate gate drives for the stacked output stage. Besides, a Gate-tracking circuit and a Floating N-well technique are adopted to prevent 1¡ÑVDD device from gate-oxide overstress problems and leakage currents. The maximum data rate is simulated to be 166/166/166/100/80 MHz when VDDIO is 5.0/3.3/1.8/1.2/0.9 V, respectively, given an equivalent probe capacitive load of 10pF. The second topic is a process, voltage, and temperature¡]PVT¡^detector for 2¡ÑVDD output buffer with slew-rate compensation. The threshold voltage¡]Vth¡^ of PMOSs and NMOSs varying with process variation could be detected, respectively. In addition, the voltage and temperature variations could be monitored, respectively, by detecting different charging and discharging times of delay buffers at each PVT corner. By adjusting output currents, the slew rate of output signals could be compensated over 24¢H. Moreover, the maximum data rate with compensation is 133 MHz in contrast with 100 MHz without compensation when VDDIO ¡× 1.8 V, in transmitting mode.