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Transistor

Transistor. Introduction. The term Transistor was derived from the word “Transfer” of “resistor” A semiconductor device that Amplifies, Oscillates, Switches Operation depends on the flow of current Lighter in weight Low operating voltage High efficiency More sensitive to shock.

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Transistor

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  1. Transistor

  2. Introduction • The term Transistor was derived from the word “Transfer” of “resistor” • A semiconductor device that • Amplifies, • Oscillates, • Switches • Operation depends on the flow of current • Lighter in weight • Low operating voltage • High efficiency • More sensitive to shock

  3. History Invention of the Transistor In 1948 • American physicists John Bardeen, Walter H. Brattain, and William Shockley (later jointly awarded a Nobel Prize) of Bell Telephone Laboratories invented Transistor • It was also independently developed nearly simultaneously by Herbert Mataré and Heinrich Welker, German physicists working at Westinghouse Laboratory in Paris. • Transistors are very durable, are very small, have a high resistance to physical shock, and are very inexpensive. • At one time, only discrete devices existed; they were usually sealed in ceramic, with a wire extending from each segment to the outside, where it could be connected to an electric circuit. • The vast majority of transistors now are built as parts of integrated circuits.

  4. BJT Transistors: NPNTransistor Sandwiching a P-type layer between two n-type layers. PNPTransistor Sandwiching a N-type layer between two p-type layers.

  5. Types Of Transistor • BJT Bipolar Junction Transistor • FET Field effect transistor

  6. How a “NPN” Transistor works? The base-emitter diode (forward) acts as a switch. when v1>0.7 it lets the electrons flow toward collector. so we can control our output current (Ic) with the input current (Ib) by using transistors. E C B backward Forward

  7. Transistors have three terminals: Collector Base Emitter Active: Always on Ic=BIb Saturation :Ic=Isaturation On as a switch Transistors work in 3 regions Off :Ic=0 Off as a switch

  8. Transistor as a Switch • Transistors can be used as switches.1 Transistor Switch • Transistors can either • conductornot conduct current.2 • ie, transistors can either be onoroff.2

  9. Transistor Switching Example15 X 12V Variable Voltage Supply • When VBE is less than 0.7V the transistor is off • and the lamp does not light. • When VBE is greater than 0.7V the transistor is on • and the lamp lights.

  10. Transistor Circuit : Light-Controlled Circuit • This transistor circuit contains • a Light-Dependent Resistor. • Because of the LDR, this circuit is dependent on light. • The purpose of this circuit is to turn on the LED when the light reaches a certain intensity. • LED = Off. • Cover LDR. • RLDR. • VLDR. • Transistor switches on. • LED = On. Input = Voltage Divider Process = Transistor Output = LED

  11. Transistor as an amplifier: Transistors are often used as amplifiers to increase input signal in radios, televisions and some other applications .The circuit may be designed to increase the current or voltage level. The power gain is the product of current gain and voltage gain (P=V*I).

  12. Amplifier example: As you see, the transistor is biased to be always on. The input signal is amplified by this circuit. The frequency of output is the same as its input, but the polarity of the signal is inverted. The measure of amplification is the gain of transistor. Example: Input Amplitude =0.2v Output amplitude=10v Gain=10/0.2=50

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