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The first CMOS family of logic integrated circuits was introduced by RCA as CD4000 COS/MOS, the 4000 series, in 1968. Initially CMOS logic was slower than LS-TTL. However, because the logic thresholds of CMOS were proportional to the power supply voltage, CMOS devices were well-adapted to battery-operated systems with simple power supplies.
NMOS AND-by-default logic can produce unusual glitches or buggy behavior in NMOS components, such as the 6502 "illegal opcodes" which are absent in CMOS 6502s. In some cases such as Commodore's VIC-II chip, the bugs present in the chip's logic were extensively exploited by programmers for graphics effects.
CMOS inverter (a NOT logic gate). Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss ", / s iː m ɑː s /, /-ɒ s /) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFETs for logic functions. [1]
In logic, a set of symbols is commonly used to express logical representation. The following table lists many common symbols, together with their name, how they should be read out loud, and the related field of mathematics.
In NMOS logic, the lower half of the CMOS circuit is used in combination with a load device or pull-up transistor (typically a depletion load or a dynamic load). AOI gates are similarly efficient in transistor–transistor logic (TTL). Examples. CMOS 4000-series logic family: CD4085B = dual 2-2 AOI gate [3] CD4086B = single expandable 2-2-2-2 ...
Current mode logic (CML), or source-coupled logic (SCL), is a digital design style used both for logic gates and for board-level digital signaling of digital data.. The basic principle of CML is that current from a constant current generator is steered between two alternate paths depending on whether a logic zero or logic one is being represented.
In logic families like TTL, NMOS, PMOS and CMOS, an AND gate is built from a NAND gate followed by an inverter. In the CMOS implementation above, transistors T1-T4 realize the NAND gate and transistors T5 and T6 the inverter. The need for an inverter makes AND gates less efficient than NAND gates.
The writing process is the easiest, the desired value logic 1 (high voltage) or logic 0 (low voltage) is driven into the bit line. The word line activates the nMOS transistor (3) connecting it to the storage capacitor (4). The only issue is to keep it open enough time to ensure that the capacitor is fully charged or discharged before turning ...