This document provides an overview of electronic devices and circuits. It discusses two forms of electronic signals - analog and digital. Analog signals are continuous representations of physical measurements, while digital signals use binary numbers. The document then lists some common applications of electronics like digital electronics, power, medical devices, automotive, industrial, and communications. It classifies electronic components as either passive or active, with passive components not amplifying or converting signals, and active components able to amplify or transform energy. Vacuum tubes are then described in more detail, including the thermionic emission process, heater types, and common tube types like diodes, triodes, tetrodes, and pentodes.

1. Electronic Devices and Circuits
Lecture
Engr. Jimmy Carter B. Nilo, RECE
January 2020
v3

2. Two Forms of Electronic Signals
• Analog Signals
– is a continuous signal which represents physical
measurements.
– E.g. Human voice in air, analog electronic devices.

3. Two Forms of Electronic Signals
• Digital Signals
– Digital signals are discrete time signals generated
by digital modulation. ( using Binary Numbers)
– E.g. Computers, CDs, DVDs, and other digital electronic
devices

4. Applications of Electronics
1. Digital Electronics
2. Electric Power
3. Medical Electronics
4. Automotive Electronics
5. Industrial Electronics
6. Communications Electronics

5. Classification of Electronics
Components
1. Passive Components
– Do not have ability to amplify a signal
– Only dissipate a power from an external source
– Does not convert electrical signals such as ac-to-dc or
vice versa.
– Stores energy ( Voltage or Current Energy)
– Linear device
– Examples:
• Resistors
• Capacitor
• Inductor/Chokes/Transformer

6. Classification of Electronics
Components
2. Active Components
- have the ability to amplify electrical signals ( increase
the energy or power)
- have the ability to transform an energy ( ac-to-dc )
- needs power source to operate properly
- Non-linear Device
-examples:
- Transistors ( BJT or FET)
- Thyristors ( SCR/TRIAC)
- Vacuum Tubes ( Diodes/Triodes/Tetrode/Pentode)
- Display Devices ( CRT/ LCD)

7. Vacuum Tubes

8. Vacuum Tubes
• Vacuum tube is an electronic device that controls
the flow of electrons in a vacuum.
• It is also called as electron tube or valve.
• John Ambrose Fleming developed the first
vacuum tube in 1904.
• Fleming’s diode allows the flow of electric current
in only one direction (from cathode to anode)
and blocks the electric current in another
direction (from anode to cathode).
• In 1907, American electrical engineer Lee De
Forest invented Audiotron vacuum tube. ( triode)

9. Vacuum Tubes
• Thermionic Emission
– The process by which free electrons are emitted
from the surface of a metal when external heat
energy is applied.
– The process occurs in metals that are heated to a
very high temperature. In other words, thermionic
emission occurs, when large amount of external
energy in the form of heat is supplied to the free
electrons in the metals.

10. Vacuum Tubes
• Types of Heater
– Directly-Heated Cathode
• The Cathode serves as heater and electron emitter

11. – In-directly Heated Cathode
• Composed of Heater and separate cathode as electron
emitter

12. Types of Vacuum Tubes
1. Diode
- converts ac signal to dc signal ( Rectifier )

13. Types of Vacuum Tubes
• Triode
– First electronic device capable of amplifying signal

14. Types of Vacuum Tubes
• Tetrode

15. Types of Vacuum Tubes
• Pentode

16. Types of Vacuum Tubes
• Pentode ( Top View)

17. THE END