No abstract

In order to seek an electro-static discharge with higher failure current per unit area and latch-up immunity, a novel multi-finger dual-direction silicon controlled rectifier (DDSCR) using the 0.5 µm complementary and double-diffusion metal-oxide-semiconductor technology was proposed. The working principle of the device is analyzed by using equivalent circuit and technology computer aided design simulation. From the test result of the transmission line pulse testing system we can see that the holding voltages for the traditional dual-direction silicon controlled rectifiers with a single-finger and two-fingers are 11.34 V and 7.63 V, respectively, which is decreased as the number of fingers increases. The holding voltage of the proposed device is 12.2 V, which is higher than that of the traditional 2-finger DDSCR and suitable for communication interface high voltage electrostatic discharge (ESD) protection. Furthermore, the influence of some dimensions, fingers and total finger width on the device is discussed. The proposed device not only solves the problem of decreasing the holding voltage caused by increasing the number of fingers, but also has a slight effect on the failure current. The root cause for such holding voltage trend is their different working mechanisms. The proposed device is turning on one finger by another instead of simultaneously turning on in the multi-finger traditional devices. Therefore, the proposed ESD device owns a holding voltage similar to that of the 1-finger device.

In this work, a class-AB operational amplifier is to be presented, which is developed in a 0.5 μm CDMOS technology. The proposed amplifier is composed of a folded cascade input stage and a class-AB output stage. Owing to the special design of the operational amplifier, the robustness of the whole circuit has been enhanced. The proposed system can drive a wide resistance load range from 10 Ω to 100 kΩ with a 10 pF capacitance load without distortion and stability problems. In addition, a current-limit technique that stems from the design of a low dropout linear regulator is adopted to protect the output stage of the operational amplifier from being damaged by a huge transient current under unexpected conditions (when the output terminal is shorted to ground or V DD). Measurement results show that the maximum output current is nearly 390 mA with an 800 mA DC current limiting protection circuit on the single 5 V power supply at room temperature. This design can stably work at the industrial temperature range from −40 to 125°C. What is more, the total static current consumption of the whole circuit is 624 μA and the chip area is 0.419 mm 2 .