Course Details: Analog Circuits and Systems
This course was the most demanding one in the third semester.I wrote as many as 123 pages of notes (including exercises, circuit structures, and records of characteristic principles) in order to achieve a satisfactory score in the final examination.The instructor, Associate Professor Lyu Shuaishuai, was very patient in both lecturing and error correction, which was one of the reasons I was able to persevere. The course content follows the main thread of "from device models to system circuit analysis," covering diodes, field-effect transistors, bipolar junction transistors, integrated operational amplifier units, power amplifiers, negative feedback, and signal generators.
Course Positioning and Learning Objectives
The course "Analog Circuits and Systems" emphasizes the integrated analysis of "model + topology + specifications": device models are used to characterize operating regions and parameter relationships, topology is used to identify circuit functions, and specifications are used to evaluate input/output characteristics and gain performance.
Circuit Recognition Ability
Upon seeing a circuit, first determine its type and configuration, such as CS/CD/CG, CE/CC/CB, differential pairs, feedback networks, and power amplifier output stages.
Modeling Ability
Switch between ideal models, constant-voltage-drop models, small-signal models, and high-frequency models in DC and small-signal scenarios to ensure the correctness of the analysis boundary.
Problem-Solving Ability
Centered on the quiescent operating point and AC specifications: solving for ID/IC, VGS/VCE, as well as key parameters such as Ri, Ro, Av, and fH.
Design Ability
Capable of deducing operational amplifier circuit parameters based on input-output relationships, and completing basic design judgments for the power amplifier output stage and feedback network.
Chapter Overview
| Chapters | Core Topics | Review Focus |
|---|---|---|
| Chapter 2: Diodes | Diode models and rectifier/limiter/voltage regulator circuits | Operating state determination, model switching, and rectification conclusion summarization |
| Chapter 3: Field-Effect Transistors | MOSFET biasing, small-signal model, CS/CD/CG configurations | Quiescent point calculation + small-signal parameter and gain computation |
| Chapter 4: Bipolar Junction Transistors | NPN/PNP amplification region analysis, CE/CC/CB configurations | Integration of DC biasing and equivalent small-signal circuits |
| Chapter 5: Operational Amplifier Units | Current sources, differential stages, multistage amplifiers, active loads, high-frequency response | Three-step approach: circuit identification, drawing, and solving + high-frequency methods |
| Chapter 6 Power Amplifiers | Class B / Class AB Output Stages | Output Power, Efficiency, Power Dissipation, and Device Selection |
| Chapter 7 Negative Feedback | Feedback Types, Configuration Determination, Deep Feedback Approximation | Instantaneous Polarity Method + Performance Impact Conclusions |
| Subsequent Application Chapters | Operational Amplifier Application Circuits, Comparators, Signal Generators, Power Supplies | Input-Output Derivation and Parameter Design Capability |
Devices and Basic Amplifier Circuits
Diodes (Chapter 2)
The key point is "state first": first determine conduction or cutoff, then select the model (ideal, constant voltage drop, piecewise linear, small-signal, Zener model), and finally solve clipping, rectification, and voltage regulation circuits.
Field-Effect Transistors and Bipolar Junction Transistors (Chapters 3–4)
With the quiescent operating point and small-signal parameters as the main focus, master the input-output characteristics, gain characteristics, and advantages/disadvantages of the three basic configurations: CS/CD/CG and CE/CC/CB.
Core Small-Signal Solution Pipeline:Configuration Determination
First identify which terminal the input and output are referenced to, then quickly locate the configuration as common-source/common-drain/common-gate or common-emitter/common-collector/common-base.
Parameter Directional Sense
Master the qualitative variations of gain and input/output resistance; prioritizing qualitative analysis before quantitative analysis can significantly reduce calculation errors.
Model Validity Range
Clearly define the applicable conditions of the model to avoid directly substituting parameters of devices in the cutoff region as if they were in the amplification region.
Problem Type Integration
A single problem often includes three sub-questions: "bias + small signal + specifications." It is recommended to draw a unified diagram and perform a one-time derivation.
Operational Amplifier Units and High-Frequency Analysis
Unit 1: Mirror/Proportional Current Source
First determine the reference branch, then obtain the output branch current using the proportional relationship, while identifying the calculation path for the output resistance.
Unit 2: Differential Amplifier Circuit
Distinguish between differential mode and common mode, establish equivalent circuits separately, and complete the derivation of Ri, Ro, and Av for both dual-ended and single-ended outputs.
Unit 3: Multistage and Active Load
Identify the function of each stage and the inter-stage coupling relationship, comprehensively solve for the total gain and input/output resistance, and pay attention to the gain enhancement brought by the active load.
Unit 4: High-Frequency Response
Focus on the high-frequency model, Miller equivalent, and open-circuit time constant method to solve for the upper cutoff frequency fH of CS/CE circuits.
Common Steps for High-Frequency Analysis:Power Amplifiers, Feedback, and Application Circuits
| Topic | Key Knowledge Points | Key Points for Problem Solving |
|---|---|---|
| Class B/AB Power Amplifier | Output stage structure, waveform characteristics, crossover distortion | Relationship between VOM and VCC, output power, efficiency, and power dissipation calculation |
| Negative Feedback | Feedback classification, configuration determination, deep feedback approximation | Use the instantaneous polarity method to determine the type, and analyze the impact on Ri/Ro/Av/bandwidth |
| Operational Amplifier Applications | Inverting amplifier, non-inverting amplifier, summing amplifier, difference amplifier, integrator, differentiator, comparator | Derive the input-output relationship using the principles of virtual short, virtual open, and superposition. |
| Signal generator and power supply | Sine/square/triangular wave circuits, voltage regulator structure | Parameter design and period expression, voltage regulation principle and output conditions |
Priority of feedback determination
First determine positive or negative feedback, then identify the voltage/current series-parallel configuration, and finally substitute into the approximate formula for calculation.
Derivation of application circuits
For operational amplifier problems, it is recommended to consistently use the nodal current method combined with virtual short and virtual open to reduce sign errors.
Power amplifier design approach
First satisfy the output swing, then verify the device current and power dissipation limits, and finally compare the trade-off between efficiency and distortion.
Waveform and parameter interaction
Be able to quickly predict the output waveform from the circuit structure, and then inversely deduce the threshold, resistor-capacitor values, and power supply parameter range.
Review Methods and Problem-Solving Strategies
The review materials for this course repeatedly emphasize: first "recognize and identify the circuit diagram," then "sketch and draw the diagram," and finally "compute and solve." Adhering to these three steps can significantly improve the efficiency of decomposing complex problems.
Step 1: Establish problem-type templates by chapter
Organize fixed analysis templates for diodes, MOSFETs, BJTs, differential amplifiers, feedback, and power amplifiers separately to avoid reconstructing the approach on the spot.
Step 2: Treat homework problems as model training
Focus on typical problems such as 3.22/3.23/3.25/3.26, 4.12/4.18/4.19/4.21, 5.8/5.12/5.14/5.18/5.23/5.24/5.35, 6.5/6.6/6.10, 8.6/8.8/8.9/8.26/8.27, and 9.7/9.8/9.11.
Step 3: Emphasize both conclusions and derivations
Memorize commonly used conclusions, and for key conclusions, be able to re-derive them from the equivalent circuit to ensure transferability to variant problems during exams.
GitHub Repository
Course-related code and materials are publicly organized in the following repository. It is recommended to first review the repository structure, and then study concurrently with the segmented PDF notes below.
ChrisChan114514/HDU-HC-OPL-analogous-circuit
Repository for Code and Materials in the Analog Electronics Course
Course Notes PDF Preview
The notes are divided into 25 PDF segments. The webpage loads Part 1 by default, and subsequent parts can be loaded by clicking a button, facilitating continuous review on the web while controlling bandwidth usage.
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