| 摘要 |
An integrated circuit having first and second N-type epitaxial layers grown over a P-type silicon substrate includes PN junction isolated pockets. In at least one pocket is a small signal device, namely an I2L transistor. In an adjacent pocket is a vertical NPN power transistor wherein the base is a P-type buried layer extending upward out of an N-type buried layer, both of which are grown from the substrate surface. The upward diffusion of the base region is substantially terminated at the interface between the epitaxial layers and thus the base width and charge are precisely controllable. Connected in the up-beta power transistor mode, the gain is precisely controllable independent of process variations made to control small signal devices. In the down-beta mode and connected as a diode with base and collector shorted, an excellent clamp diode is made producing an unusually low parasite current in the substrate.
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