In an ESD protection circuit, diodes for shunting current through an ESD clamp
include a third terminal in order to provide a dual current path through the diode
structure and provide for a voltage drop to the input of the protected internal
circuit. In another embodiment, where a bipolar junction transistor is used as
an ESD clamp to shunt current to ground between an I/O pad and an input to a protected
internal circuit, a lower voltage is provided to the internal circuit by providing
a voltage drop across an internal resistive element of the bipolar junction transistor.
This is achieved by making use of two base terminals, one connected to the I/O
pad, and the other connected to the input of the internal circuit and spaced from
the first contact by the base polysilicon region of the bipolar junction transistor.
