CMOS

Complementary Metal-Oxide - Semiconductor (English, to complementary metal oxide semiconductor "), abbreviation CMOS, is a designation for semiconductor devices, in which both p-channel and n -channel MOSFETs may be used on a common substrate.

In CMOS technology, and technology is meant

The technique was developed in 1963 by Frank Wanlass semiconductor manufacturer Fairchild Semiconductor and patented.

Technology

The basic principle of the CMOS technology in digital technology, the combination of p- channel and n -channel field effect transistors. In this case, the desired logical operation on the one hand p-channel technology ( as a pull -up path) and the other n- channel technology is developed ( as a pull- down path ) and brought together in a circuit. By the same control voltage, respectively of two complementary transistors (one n-channel, one p-channel ) is always exactly one locked and the other is conductive. A low voltage of approximately 0 V at the input ( E) of the inverter corresponds to the logic "0". It ensures that only the p- channel device conducts current, and hence the supply voltage to the output ( A) is connected. The logical "1" corresponds to a higher positive voltage ( in modern circuits > 1 V) and causes only the n-channel component passes, and thus the mass is connected to the output.

Compared to the NMOS logic although twice the number of transistors must always be applied to a chip, since the operating resistance of the NMOS implementation in CMOS is replaced by a PMOS transistor., The PMOS transistor can be integrated into ICs but lighter than a resistor. A resistor also produces unwanted heat, as long as the transistor is conducting. There is no need for resistors in the CMOS technology, in contrast to NMOS technology, an advantage arises: the flow ( from the supply voltage to ground ), flows only in the switching instant. ( In the NMOS realization there is the problem that in the conducting state " the strong zero " (0 )! Angle! Against " the weak one" (H )! Impose from the top! Needs (see IEEE 1164 ) and thereby continuously a current flows from the top, as long as the transistor remains conductive ) the power consumption or power dissipation is thus -. apart from the much smaller leakage current - only by the switching frequency ( clock speed), and the signal to noise ratio dependent. For this reason, most digital ICs ( processors, memory ) are currently being made ​​in this technology. The power dissipation is also linearly dependent on the clock frequency and the square of the signal to noise ratio dependent (see chart).

For analog applications, the high integration and the capacitive control can be used to enable the MOSFETs. By saving of the resistors and the use of active loads ( current mirror as sources or sinks) noise dependencies and other undesirable effects can be reduced to a minimum. Through a wide frequency bandwidth of the components in high integration very broadband circuits can be created.

Properties

The power loss at rest is usually about 10 nW, the power dissipation during switching frequency and operating voltage is dependent, depending on building type in standard series at about 1 mW / MHz (integrated gate: about 10 uW / MHz).

Unlike logic blocks of the TTL family who work at 5V, the typical operating voltage is from 0.75 to 15 V.

CMOS inputs are sensitive to static electricity and surge voltages, so (for example, diodes to the two operating voltages) to be placed in front of the CMOS input, if technically possible, one or two-stage protective circuit. Furthermore, in CMOS circuits, and in the event of voltages at the inputs of the problem of the so-called " latch -up ".

Specific species

HC / HCT CMOS

With HC - CMOS technology ( H for high speed ) refers to the development of the CMOS logic family 4000, in order to achieve the velocity of the LS- TTL family. However, HC inputs are not compatible with TTL output levels. Therefore, the HCT -well CMOS technology was developed, in which the CMOS transistor structure has been adapted to the output voltage level of the TTL family at full pin compatibility therewith. An exchange of TTL circuits with HCT- CMOS circuits is therefore possible.

BiCMOS

Of the BiCMOS technology is defined as a circuit technique can be combined with the field-effect transistors with bipolar transistors. Both the input and the logic combination can be realized in CMOS technology, - with the corresponding advantages. However, bipolar transistors are used for the output stage. This brings a high current driving capability with himself and a small dependence of the capacitive load. Here are two more transistors and two resistors in the circuit are needed in logic circuits typically. Input behavior corresponds to a CMOS circuit, the spending behavior of a TTL circuit.

With BiCMOS succeeds continue to combine logic circuits with power electronic circuit components on a chip. Examples are switching regulator that can be powered directly from the rectified mains voltage.

Areas of application

CMOS technology is by its very low power consumption for the production of integrated circuits. These are used in all areas of electronics, such as digital clocks, or in automotive electronics. Also, be made ​​(for example, photo-detectors in the form of CMOS sensors for digital photography or spectroscopy ) with her memory elements, microprocessors and sensors.

Also for analog applications, the CMOS technology is employed. So CMOS operational amplifiers are available, which are characterized by an extremely high input impedance and low supply voltage.