CMOS LSI circuit with dual-purpose contacts - has complementary transistor pair responding to level change greater than that needed by buffer

摘要

The CMOS LSI circuit overcomes the problem of having too few external contacts for the internal contacts by using certain contacts for different functions e.g. to handle input voltages lying in different ranges. The external input contact (7) is connected via a protective circuit to a buffer (9) and to a complementary pair of MOSFETs (Q1, Q2) whose output is connected to the input of control logic (30). The external output contact (21) is connected directly to the logic. The buffer drives system control logic (40). The control logic connects either an internal input or output (27, 25) of the system logic to the external output contact.