Therefore, it is important to emphasize that this course is a technical foundation subject, with the word "technical" being central. While qualitative understanding of concepts is essential, the course also focuses on quantitative estimation. Due to the inherent variability in semiconductor device parameters—such as resistors and capacitors often having tolerances of more than ±5%—it is impractical to pursue overly precise calculations. As a result, students should be trained in approximate calculation methods and problem-solving strategies commonly used in engineering practice. Moreover, since this is a highly practical course, the experimental component must not be overlooked. It is crucial to integrate theory with hands-on experience, helping students develop both their electronic technology skills and their ability to conduct experimental research.
First, the fundamentals of amplifier circuits.
As the starting point of the course, there are many new concepts introduced at the beginning, and it is essential for students to build a solid foundation in analysis and calculation techniques. Therefore, the pace of instruction should be moderate, ensuring enough time is allocated for thorough understanding.
Regarding the physical basis of semiconductors, this has already been covered in previous courses such as Physics and Chemistry. Therefore, we will not repeat those topics but instead introduce them from the perspective of crystal covalent bonds. The PN junction is a core topic, and students should understand its unidirectional conductivity, current distribution, and amplification mechanism. Special attention should be given to the characteristics and key parameters of diodes and transistors.
1. Among the three basic amplifier configurations (common-emitter, common-base, and common-collector), the focus should be on the common-emitter and common-collector circuits, including their structure and working principles.
2. Graphical analysis is an effective method for determining the static operating point and analyzing dynamic behavior, but it is not necessary to calculate the voltage gain directly.
3. The small-signal equivalent circuit method is a fundamental tool for amplifier analysis. Students should thoroughly understand the derivation of hybrid-parameters, the construction of equivalent circuits, and the concept of controlled sources. They should be able to compute the voltage gain, input resistance, and output resistance using the h-parameter model. Mastery of these tools through various teaching activities is essential.
4. When discussing the stabilization of the operating point in amplifiers, the emitter bias circuit is the primary method. For the collector-base bias circuit, a brief explanation of its stabilization mechanism is sufficient, and students can explore it further if needed. Miller’s theorem, which is useful for high-frequency approximation, can be introduced in exercises or guided reading. It plays an important role in analyzing frequency characteristics and is also used to explain the concept of Miller capacitance. Additionally, it helps in understanding how time constants change in op-amp-based integrator and differentiator circuits.
5. After introducing the emitter bias circuit, the constant current source can be presented as a key component. It is widely used in discrete-component circuits and even more frequently in analog integrated circuits.
6. In addition to the basic common-collector configuration, it is beneficial to introduce the concept of the composite bootstrap follower and composite transistor, which are commonly found in power amplifiers and power supplies. The bootstrap technique is also widely applied in various practical circuits.
Second, FET amplifiers.
The Field-Effect Transistor (FET) is a unipolar device. This section covers the JFET and its amplifier circuits. The insulated-gate FET (IGFET) and its amplifier circuits can be compared with the standard FET circuits to highlight differences and similarities.
The Junction Field-Effect Transistor (JFET) is based on a PN junction. Students should become familiar with its structure, working principle, characteristic curves, main parameters, and usage considerations.
For FET amplifiers, the purpose of the biasing circuit and AC signal control (input voltage to output current) should be clearly explained. Given the variability in device characteristics, the formula-based approach is emphasized when analyzing the operating point. When evaluating performance metrics like gain, the small-signal equivalent circuit method is used.
Third, frequency characteristics and multi-stage amplifiers.
1. In this section, it is essential to first study the background, purpose, and significance of amplifier frequency characteristics. Students should understand how DC blocking capacitors and emitter bypass capacitors affect low-frequency performance, as well as how junction and wiring capacitances influence high-frequency behavior.
2. To simplify the analysis, RC high-pass and low-pass circuits can be used to demonstrate the Bode plot method for approximating frequency responses. Then, the RC-coupled amplifier can be treated as a combination of high-pass and low-pass circuits for analysis.
3. When analyzing the low-frequency response of a common-emitter circuit, the effect of the emitter bypass capacitor on the input loop is usually dominant. The output loop is less affected, and the lower cutoff frequency is determined by the larger of the two time constants.
4. When discussing high-frequency characteristics, the focus should be on the high-frequency parameters of the hybrid-Ï€ equivalent circuit and the transistor.
5. The transient response of a single-stage amplifier may not be required unless specifically requested.
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