In integrated circuit technologies, BiCMOS, also called BiMOS, refers to the integration of bipolar junction transistors and CMOS technology into a single device. This technology has commercial application in amplifier and discrete component logic design. Integrated circuit showing memory blocks, logic and input/output pads around the periphery Microchips with a transparent window showing the integrated circuit inside. ... A bipolar junction transistor (BJT) is a type of transistor. ... Static CMOS Inverter Complementary-symmetry/metal-oxide semiconductor (CMOS) (see-moss, IPA:), is a major class of integrated circuits. ... Generally, an amplifier is any device that uses a small amount of energy to control a larger amount of energy. ...

History

Historically, integrating bipolar and MOS transistors into a single device proved difficult and uneconomical. For this reason, until now most integrated circuits have used one or the other, according to application requirements. Particularly, bipolar transistors offer high speed, high gain, and low output resistance, whereas CMOS technology offers high input resistance, which translates to simple, low-power logic gates. For years designers of circuits utilizing discrete components have realized the advantages of integrating the two technologies; however, lacking implementation in integrated circuits, application was restricted to fairly simple designs. In electronics, gain is usually taken as the mean ratio of the signal output of a system to the signal input of the system. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... For delivered electrical power, see Electrical power industry. ... A logic gate performs a logical operation on one or more logic inputs and produces a single logic output. ...

In the 1990s, modern IC fabrication technologies began to make BiCMOS a reality. This technology rapidly found application in amplifiers and 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 MOSFETs for efficient control, and portions of specialized very high performance circuits use bipolar devices. Examples of this include RF oscillators, bandgap-based references and low noise circuits. The 1990s decade refers to the years from the start of 1990 to the end of 1999. ... Look up analog, analogue in Wiktionary, the free dictionary. ...

Advantages

MOS circuits are ideally suited for use in logic (digital) applications because of their low current consumption. Bipolar devices are critical for creating accurate voltage references and when very low noise is required. MOS devices (power FETs) are also used extensively in BiCMOS ICs for switching or regulating high currents as this can be done easily with low complexity control circuits. Freescale Semiconductor's SMARTMOS[1] process is an example of a commercially successful BiCMOS process which uses the characteristics of the different transistors very effectively.

Difficulties

BiCMOS as a fabrication process is not nearly as mature as either BJT or CMOS fabrication. Unfortunately, many of the improvements to CMOS fabrication, for example, do not transfer directly to BiCMOS fabrication. An inherent difficulty arises from the fact that fine tuning of both the BJT and MOS components is impossible without adding many extra fabrication steps, and consequently increasing the cost. Finally, in the area of high performance logic, BiCMOS may never offer the (relatively) low power consumption of CMOS alone.

See also

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