Bipolar Junction Transistors (BJTs).pptx

Bipolar Junction Transistors

1. Bipolar Junction Transistors (BJTs) Reference: Microelectronic circuits by Sedra and Smith, Oxford Publishing . 13-08-24 1 Presented by Sarika A S

2. In this Presentation, The Physical structure of the bipolar transistor and how it works. How the voltage between two terminals of the transistor controls the current that flows through the third terminal. The output Characteristics of Common Emitter Configuration of an NPN transistor. 13-08-24 2

3. Bipolar Junction Transistor BJT was invented in 1948 at bell Telephone Laboratories. New era of Solid-state circuits It was replaced by MOSFET as predominant transistor used in modern electronics . The first commercial transistor was made by Texas Instruments in 1954. Bipolar - transistor contains two types of semiconductor material — one positive type (p-type) and one negative type (n-type) — through which a current flows. BJT refers to a three-terminal semiconductor device consisting of two p-n-junctions that are formed by sandwiching either p-type or n-type semiconductors between two n-type or p-type semiconductors . Active and Linear electronic device. 13-08-24 3

4. Device Structure and P hysical Operation BJT consist of three semiconductor regions: Emitter region Base region Collector region Transistor consist of two pn -junctions : Emitter Base Junction Collector base junction 13-08-24 4 Types of BJT: NPN Transistor PNP Transistor

5. Transistor Biasing and Modes of operation Operating mode depends on biasing Active mode – Used for amplification Cutoff and saturation modes – used for switching 13-08-24 5

6. Symbol and operation of NPN Transistor 13-08-24 6 Three Configurations: Common Base Configuration   –   has Voltage Gain but no Current Gain. Common Emitter Configuration   –   has both Current and Voltage Gain. Common Collector Configuration   –   has Current Gain but no Voltage Gain.

7. The Common Emitter (CE) Configuration In the  Common Emitter  or grounded emitter configuration, the input signal is applied between the base and the emitter, while the output is taken from between the collector and the emitter. The common emitter amplifier configuration produces the highest current and power gain of all the three bipolar transistor configurations . This is mainly because the input impedance is LOW as it is connected to a forward biased PN-junction, while the output impedance is HIGH as it is taken from a reverse biased PN-junction. 13-08-24 7

8. Output characteristic of CE amplifier 13-08-24 8

9. Thank You 13-08-24 9