| 摘要 |
A Zener diode (D) exhibiting subsurface breakdown includes a cathode (36) formed entirely within the emitter (22, 28) of a vertical PNP transistor (Q). The base (16) and collector (11) of the PNP transistor are resistively coupled to ground. The emitter of the PNP transistor functions as the anode of the Zener diode. Because of this, it is unecessary to provide an emitter contact. The PNP transistor compensates for changes in Zener breakdown voltage caused by changes in temperature. Because the PNP transistor is formed directly underneath the Zener diode, the temperature of the PNP transistor accurately tracks that of the Zener diode and therefore provides better temperature compensation. Also, because the cathode of the Zener diode is formed directly in the emitter of the PNP transistor, there is no lateral current flow and attendant voltage drop in the emitter of the PNP transistor.
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