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'''BiCMOS''' is an evolved semiconductor technology that integrates two formerly separate semiconductor technologies - those of the analog [[bipolar junction transistor]] and the digital [[CMOS]] transistor - in a single [[integrated circuit]] device.

Bipolar junction transistors offer high speed, high{{Citation needed|date=February 2008}} [[gain]], and low output [[electrical resistance|resistance]], which are excellent properties for high-frequency [[analog amplifier]]s, whereas CMOS technology offers high [[input resistance]] and is excellent for constructing simple, low-[[electric power|power]] [[logic gate]]s.  For as long as the two types of transistors have existed in production, designers of circuits utilizing discrete components have realized the advantages of integrating the two technologies; however, lacking implementation in integrated circuits, the application of this free-form design was restricted to fairly simple circuits.  Discrete circuits of hundreds or thousands of transistors quickly expand to occupy hundreds or thousands of square centimeters of circuit board area, and for very high-speed circuits such as those used in modern digital computers, the distance between transistors (and the minimum [[capacitance]] of the connections between them) also makes the desired speeds grossly unattainable, so that if these designs cannot be built as integrated circuits, then they simply cannot be built.

In the 1990s,{{Citation needed|date=February 2008}} modern integrated circuit fabrication technologies began to make BiCMOS a reality.  This technology rapidly found application in amplifiers and [[analog electronics|analog]] power management circuits, and has some advantages in digital logic. BiCMOS circuits use the characteristics of each type of transistor most appropriately. Generally this means that high current circuits use metal–oxide–semiconductor field-effect transistor ([[MOSFET]]s) for efficient control, and portions of specialized very high performance circuits use bipolar devices. Examples of this include radio frequency (RF) oscillators, [[bandgap]]-based references and low-noise circuits.  The [[Intel P5|Pentium]], [[Pentium Pro]], and [[SuperSPARC]] microprocessors also used BiCMOS.{{Citation needed|date=February 2008}}

== Disadvantages ==
BiCMOS as a fabrication process is not currently as commercially viable for some applications, such as [[microprocessors]], as with exclusively [[BJT]] or CMOS fabrication. Unfortunately, many of the advantages of CMOS fabrication, for example, do not transfer directly to BiCMOS fabrication.  An inherent difficulty arises from the fact that optimizing both the BJT and MOS components of the process is impossible without adding many extra fabrication steps and consequently increasing the process cost.  Finally, in the area of high performance logic, BiCMOS may never offer the (relatively) low power consumption of CMOS alone, due to the potential for higher standby leakage current.  An exclusive mix of BiCMOS and CMOS has appeal if the performance attributes of each type of gate can be optimized.  But since CMOS is already ideal for pure digital logic, this is only a serious issue when it is desirable to put logic circuits together on the same chip with other circuits that are not strictly logic: either for the purpose of a [[mixed-signal]] application, or simply to reduce the chip count in an electronic product by combining two chips into one, in order to reduce cost, size, and/or weight.

{{Logic Families}}
[[Category:Logic families]]

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