PMOS

The abbreviation PMOS represents English "p -channel metal-oxide semiconductor " ( German: p- channel metal -oxide-semiconductor ), and referred to in microelectronics a metal-oxide - semiconductor field effect transistor (MOSFET ) in the positively charged carrier ( electron holes ) are used to conduct the electric current through the channel ( p- channel MOSFET or PMOSFET mentioned ). Circuits that only the p-channel MOSFET used as a PMOS transistors are referred to as logic. It represents the complement of the logic NMOS (n- channel metal-oxide -semiconductor ), to take advantage of the electron conduction of the electrical current.

Technology

The majority charge carriers - roughly speaking the dominant charge carrier is based on the movement of the function - the PMOSFET are defect electrons (holes), rather than electrons in the NMOSFET. This results in that the transistor channel of PMOSFETs of the enrichment type of an n- doped and a depletion type PMOSFET of a p- doped semiconductor material.

Since electrons have a defect about three times less effective charge carrier mobility than electrons, exhibit PMOS transistors with the same dimensions by this factor approximately a lower shift speed than NMOS transistors. The circuits that use only PMOS Tranistoren are summarized under the term PMOS technology. Although PMOS circuits were initially easier to produce, they were due to this drawback, in the mid- 1970s displaced by the NMOS technology.

Since the active transistors operate both in pure PMOS technology as well as of the pure NMOS technology with a passive load resistor flows during normal operation, a current, which causes a non-negligible power required for the overall circuit. This can be significantly reduced if the load resistors to be replaced by active transistors connected to the respective complementary technology. This is in the currently dominant CMOS technology ( complementary metal-oxide -semiconductor, German complementary metal oxide semiconductor ), a circuit combination of PMOS and NMOS transistors realized.

As for the common use in a CMOS circuit, the PMOS and NMOS transistors should have similar electrical properties, the PMOS transistors are dimensioned differently in general, for example, they have a larger transistor width. In modern circuits comprise PMOS transistors further differences to NMOS transistors, the charge carrier mobility is a distortion of the channel material is increased (see Stretched silicon) or of the gate structure is provided for each type of transistor optimized (material, doping, etc.). The latter won especially with the introduction of high-k metal gate technology in importance.

Applications

PMOS technology was the first economically producible MOS IC technology. Thus, for example, the Intel 4004, the first microprocessor manufactured in series, produced in PMOS technology. Many products were produced later functionally compatible in NMOS. Examples include UARTs, keyboard controller or microprocessor SC / MP by National Semiconductor. Because of the low production costs, PMOS products could keep long time in applications such as calculators, remote controls or watch circuits in which it did not arrive at higher speed or low power consumption.