1 / 16

From analog to digital circuits

From analog to digital circuits. A phenomenological overview. Bogdan Roman. Outline. Insulators, conductors and semiconductors Semiconductor diodes: the p-n junction The Field Effect Transistor (FET): The Junction FET (JFET) The Metal Oxide Semiconductor FET (MOSFET) The MOS Inverter

lacy
Download Presentation

From analog to digital circuits

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. From analog to digital circuits A phenomenological overview Bogdan Roman

  2. Outline • Insulators, conductors and semiconductors • Semiconductor diodes: the p-n junction • The Field Effect Transistor (FET): • The Junction FET (JFET) • The Metal Oxide Semiconductor FET (MOSFET) • The MOS Inverter • Resistive and same MOS type • Complementary MOS (CMOS) technology • Elementary gates • Flip-flops • Examples Loosely based on the IA and 3B Engineering dept. courses (Linear Circuits and Devices, Digital Circuits,Information Processing, Integrated Digital Electronics)

  3. Insulators and conductors

  4. Semiconductors: Intrinsic silicon At room temperature, the thermal energy kT ~ 1/40 eV is enough to break a few covalent bonds to produce free electrons. This also leaves holes(i.e. positive net charges left by the broken covalent bond). Both electrons and holes contribute to current flow. At low temperatures, silicon is an insulator since there is not enough thermal energy to break the covalent bonds.

  5. Semiconductors: Extrinsic silicon

  6. Reverse biased diode: Forward biased diode: The p-n junction: The diode

  7. Reverse biased diode: Forward biased diode: The Diode (contd.)

  8. The Junction Field Effect Transistor (JFET) - Proposed by Shockley in 1951 - First made by Teszner in 1958 in France JFET Interactive (opens browser)

  9. Metal Oxide Semiconductor FET (MOSFET) • - First made in 1960 at Bell Laboratories in the USA by Atalla and Kahng. • Offers extremely high component density in integrated circuits. • - Very high input resistance, low noise, simpler fabrication than bipolar transistors. MOSFET Interactive (opens browser)

  10. The NMOS inverter Resistive load: NMOS load: • When input is low (0) then T1 is off, hence output goes high (1) (i.e. VDD) • When VIN = high (1) then T1 conducts (linear region) and brings the output low (0), depending on RL • High RL = low logic zero and low power consumption but large area on silicon and slow switching => compromise • T2 has the gate tied to its drain and is always on (and in saturation). Acts as a pseudo-resistor load. • Similar operation to the resistive load inverter • Smaller area on silicon (so easier to manufacture) and faster switching but has a lower high logic voltage (VDD – VT), and high power consumption when input high.

  11. Complementary MOS (CMOS) inverter In CMOS technology, the output is clamped to one of the power rails by a conductive (on) device, while the other device serves as a load of effectively infinite resistance (off). This leads to static properties that approximate those of the ideal inverter. - The PMOS devices is slower (lower mobility of holes) so it has to be larger to compensate. It is also more complex to manufacture.

  12. NOR and NAND gates The 74HC02 IC has four 2-input NOR gates The 74HC00 IC has four 2-input NAND gates

  13. Flip-flops and clocked flip-flops  =

  14. Multiplexer A crucial circuit, vital for implementing functions:

  15. Binary Counter

  16. Real stuff

More Related