FILTER CIRCUITS FOR PROTECTING AGAINST TRANSIENT ELECTRICAL PULSES

摘要

The present invention teaches a variety of filter circuits for protecting against transient electrical pulses such as those caused by electrostatic discharge (ESD) events. One aspect of the present invention teaches an integrated circuit package having primary circuitry, an ESD protection device, a filter circuit, and a conductive lead arranged to couple a point external to the integrated circuit package to a point internal to the integrated circuit package. The ESD device, coupled in series between the conductive lead and a ground reference, can limit the voltage magnitude of a transient electrical pulse occurring upon the conductive lead. The filter circuit is operable such that the voltage magnitude of an electrical signal generated at the filter circuit output is less than the voltage magnitude of the certain transient electrical pulse itself. One preferred filter circuit has two resistors R.sub.1 and R.sub.2, two capacitors C.sub.1 and C.sub.2, and two transistors Q.sub.1 and Q.sub.2. These components are arranged such the first terminals of resistors R1 and R2 and the collector of transistor Q1 are electrically coupled and constitute the filter circuit input. The second terminal of the resistor R2 and the first terminal of the capacitor C2 are electrically coupled. The second terminal of the capacitor C2 and the base of the transistor Q2 are electrically coupled. The second terminal of the resistor R1, the collector of the transistor Q2, the first terminal of the capacitor C1, and the base of the transistor Q1 are electrically coupled. Finally, the emitter of the transistor Q2 and the second terminal of the capacitor C1 are electrically coupled.