ch04 - Fundamentals of Microelectronics CH1 CH2 CH3 CH4 CH5...

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1 Fundamentals of Microelectronics CH1 Why Microelectronics? CH2 Basic Physics of Semiconductors CH3 Diode Circuits CH4 Physics of Bipolar Transistors CH5 Bipolar Amplifiers CH6 Physics of MOS Transistors CH7 CMOS Amplifiers CH8 Operational Amplifier As A Black Box
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2 Chapter 4 Physics of Bipolar Transistors 4.1 General Considerations 4.2 Structure of Bipolar Transistor 4.3 Operation of Bipolar Transistor in Active Mode 4.4 Bipolar Transistor Models 4.5 Operation of Bipolar Transistor in Saturation Mode 4.6 The PNP Transistor
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CH4 Physics of Bipolar Transistors 3 Bipolar Transistor In the chapter, we will study the physics of bipolar transistor and derive large and small signal models.
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CH4 Physics of Bipolar Transistors 4 Voltage-Dependent Current Source A voltage-dependent current source can act as an amplifier. If KR L is greater than 1, then the signal is amplified. L in out V KR V V A - = =
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CH4 Physics of Bipolar Transistors 5 Voltage-Dependent Current Source with Input Resistance Regardless of the input resistance, the magnitude of amplification remains unchanged.
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CH4 Physics of Bipolar Transistors 6 Exponential Voltage-Dependent Current Source A three-terminal exponential voltage-dependent current source is shown above. Ideally, bipolar transistor can be modeled as such.
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CH4 Physics of Bipolar Transistors 7 Structure and Symbol of Bipolar Transistor Bipolar transistor can be thought of as a sandwich of three doped Si regions. The outer two regions are doped with the same polarity, while the middle region is doped with opposite polarity.
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CH4 Physics of Bipolar Transistors 8 Injection of Carriers Reverse biased PN junction creates a large electric field that sweeps any injected minority carriers to their majority region. This ability proves essential in the proper operation of a bipolar transistor.
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CH4 Physics of Bipolar Transistors 9 Forward Active Region Forward active region: V BE > 0, V BC < 0. Figure b) presents a wrong way of modeling figure a).
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CH4 Physics of Bipolar Transistors 10 Accurate Bipolar Representation Collector also carries current due to carrier injection from base.
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CH4 Physics of Bipolar Transistors 11 Carrier Transport in Base
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CH4 Physics of Bipolar Transistors 12 Collector Current Applying the law of diffusion, we can determine the charge flow across the base region into the collector. The equation above shows that the transistor is indeed a
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ch04 - Fundamentals of Microelectronics CH1 CH2 CH3 CH4 CH5...

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