From analog to digital circuits
This presentation is the property of its rightful owner.
Sponsored Links
1 / 16

From analog to digital circuits PowerPoint PPT Presentation


  • 44 Views
  • Uploaded on
  • Presentation posted in: General

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

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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


From analog to digital circuits

From analog to digital circuits

A phenomenological overview

Bogdan Roman


Outline

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)


Insulators and conductors

Insulators and conductors


Semiconductors intrinsic silicon

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.


Semiconductors extrinsic silicon

Semiconductors: Extrinsic silicon


The p n junction the diode

Reverse biased diode:

Forward biased diode:

The p-n junction: The diode


The diode contd

Reverse biased diode:

Forward biased diode:

The Diode (contd.)


The junction field effect transistor jfet

The Junction Field Effect Transistor (JFET)

- Proposed by Shockley in 1951

- First made by Teszner in 1958 in France

JFET Interactive (opens browser)


Metal oxide semiconductor fet mosfet

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)


The nmos inverter

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.


Complementary mos cmos inverter

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.


Nor and nand gates

NOR and NAND gates

The 74HC02 IC has four 2-input NOR gates

The 74HC00 IC has four 2-input NAND gates


Flip flops and clocked flip flops

Flip-flops and clocked flip-flops

=


Multiplexer

Multiplexer

A crucial circuit, vital for implementing functions:


Binary counter

Binary Counter


Real stuff

Real stuff


  • Login