High Gain Switching PNP Transistor Compatible With Advanced NPN Technology
Original Publication Date: 1979-Mar-01
Included in the Prior Art Database: 2005-Feb-19
PNP devices often limit circuit performance due to their poor characteristics compared with NPN structures. Current gain is low (beta about 2-10) and transient performance is slow (f(T) less than 30 MHz). Additionally lateral devices require large chip area and can only draw relatively low currents. Parasitic PNP transistors, too, have poor properties and are of limited use in circuitry because the substrate is required as common collector. Other vertical approaches to improve the PNP performance use two epitaxial steps, one N and one P step, or two N steps, and N type as well as P type buried layers. They are far too complex to become a feasible complementary technology. Furthermore, they end up with processing steps which are no longer optimized with respect to the NPN performance.