01 Basics of Analog Circuits
1.1 Basic Components (Characteristics, Applications, Selection):
Resistors: Voltage division, current limiting, pull-up/pull-down, impedance matching. Understand Ohm’s law, power calculation, packaging and power relationship. Reading color-coded resistors.
Capacitors: AC coupling, filtering (decoupling/bypass), energy storage, timing. Understand capacitive reactance, charging and discharging processes, ESR, dielectric types (ceramic, electrolytic, tantalum capacitors) and application scenarios (high frequency/low frequency, large capacity).
Inductors: DC resistance, AC filtering (LC filtering), energy storage (switching power supply), transient suppression. Understand inductive reactance.
Diodes:
Rectifier Diodes: AC to DC conversion principle.
Voltage Regulator Diodes (Zener Diodes): Voltage regulation principle, current limiting resistor calculation.
Schottky Diodes: Low forward voltage drop, high-speed switching, commonly used for reverse polarity protection and flyback.
Light Emitting Diodes: Driver circuit (current limiting resistor calculation), current-voltage characteristics.
TVS Diodes: Transient voltage suppression, ESD protection principle.
Transistors (BJT / MOSFET):
BJT (NPN/PNP): Current amplification principle (Ib controls Ic), three operating states (active, saturation, cutoff). Basic switching circuit, driving small loads (such as relays, LEDs).
MOSFET (N-MOS/P-MOS): Voltage control principle (Vgs controls Ids), on-resistance, fast switching speed, low power consumption. Gate drive requirements (drive voltage, current, protection against breakdown).
Basic principles of H-bridge motor drive. Focus on the application of MOSFETs in power switching and motor control.
Optocouplers: Electrical isolation principle. Input side (LED) drive, output side (phototransistor) characteristics. Applications in isolated communication, digital input/output.
1.2 Basic Circuits:
Voltage Divider Circuit: Principle, calculation (Ohm’s law), applications in voltage sampling, reference voltage generation.
RC Circuit:
Low-Pass Filtering: Filtering out high-frequency noise (core principle of decoupling capacitors). Understand cutoff frequency calculation.
High-Pass Filtering: Filtering out DC or low frequency.
Integrator/Differentiator Circuits: Understand basic concepts.
Delay Circuits: Utilizing capacitor charging and discharging.
LC Circuits: Resonance principle, applications in filtering and oscillating circuits.
Voltage Follower (Op-Amp): High input impedance, low output impedance, used for buffering/isolation of signals. Understand the concepts of virtual short and virtual open.
Comparator (Op-Amp): Comparing two voltages, output high or low level. Understand the anti-jitter principle of hysteresis comparators (Schmitt triggers).
02 Basics of Digital Circuits
Basic Logic Gates: AND, OR, NOT, NAND, NOR, XOR, XNOR. Truth tables, logical expressions, symbols. Understand the universality of NAND/NOR.
Combinational Logic Circuits:
Encoders/Decoders: Basic principles and applications (e.g., address decoding).
Multiplexers/Demultiplexers: Data selection and distribution.
Adders: Half adder, full adder.
Sequential Logic Circuits:
Latches: Basic SR latch principle (level-triggered).
Flip-Flops: Core storage elements!
D Flip-Flop: Most commonly used! Understand clock rising/falling edge triggering, setup time, hold time concepts.
JK Flip-Flop: More flexible functionality (can act as T flip-flop).
Registers: Composed of multiple D flip-flops, temporarily store data.
Counters: Asynchronous counters, synchronous counters principles and applications (frequency division, timing).
Shift Registers: Serial-to-parallel conversion, parallel-to-serial conversion.
Bus Concept: Data bus, address bus, control bus. Understand the role of tri-state buffers in achieving bus sharing in high-impedance state.
Timing Concepts: Setup time, hold time, clock jitter, clock skew. These are key in high-speed digital circuit design! Understand their impact on system stability.
03 Power Circuits
3.1 LDO (Low Dropout Linear Regulator):
Principle: Series pass transistor (BJT), maintains constant output voltage through feedback loop.
Characteristics: Simple structure, low noise, low ripple, low cost, simple peripheral circuits (input/output capacitors).
Disadvantages: Low efficiency (power loss=(Vin-Vout)*Iout), significant heat generation, input-output voltage difference cannot be too small (limited by the LDO’s dropout voltage).
Applications: Powering noise-sensitive circuits (e.g., analog sensors, PLL, ADC reference sources), low current supply, scenarios with small voltage differences.
Key Parameters: Input voltage range, output voltage, maximum output current, dropout voltage, quiescent current, PSRR (Power Supply Rejection Ratio), noise.
3.2 DC-DC (Switching Regulator):
Principle: Uses switching devices (MOSFET) rapid on/off and inductive/capacitive energy storage/release to achieve voltage conversion (Buck step-down / Boost step-up / Buck-Boost step-up/down).
Characteristics: High efficiency (typically >80%, even >90%), low heat generation, can step up, step down, or step up/down.
Disadvantages: Complex circuitry (requires inductors, diodes/synchronous MOSFETs, input/output capacitors), higher noise and ripple, higher cost, EMI issues.
Types:
Buck (Step-Down): Most common, Vin > Vout.
Boost (Step-Up): Vin < Vout.
Buck-Boost (Step-Up/Step-Down): Vin can be greater or less than Vout (polarity may be reversed).
Charge Pump: Uses capacitive energy storage, can achieve small current step-up, step-down, or negative voltage without inductors.
Key Parameters: Input voltage range, output voltage (adjustable/fixed), maximum output current, efficiency, switching frequency, ripple.
Selection Considerations: Efficiency requirements, input-output voltage relationship, current demand, cost, size, noise requirements.
Power Integrity:
Decoupling Capacitors: Why are they needed (to provide large current required by chips instantaneously, suppress power supply noise)? How to place them (close to chip power pins)? Value selection (usually multiple different values in parallel, such as 10uF + 0.1uF + 0.01uF)? Understand their “reservoir” effect.
Power Path Design: Avoid ground bounce/power bounce. Understand the concepts and purposes of “star grounding”, “single-point grounding”, and “ground planes” (minimize ground loop impedance, reduce noise coupling).
04 Signal Processing and Interface Circuits
4.1 Op-Amp Applications:
Inverting/Non-Inverting Amplifiers: Gain calculation, input/output impedance characteristics.
Differential Amplifiers: Suppress common-mode noise, used for sensor signal reading (e.g., bridge circuits).
Instrumentation Amplifiers: High common-mode rejection ratio, high input impedance differential amplifiers.
Active Filters: Low-pass, high-pass, band-pass (understand basic concepts and uses).
4.2 ADC/DAC Peripheral Circuits:
ADC Front-End: Signal conditioning (amplification, attenuation, filtering), necessity of anti-aliasing filtering (low-pass).
Reference Voltage: Importance (directly affects accuracy), stability requirements (usually powered by dedicated Ref IC or LDO), decoupling.
DAC Back-End: May require a buffer (op-amp) to drive loads.
4.3 Sensor Interfaces:
Resistive (e.g., thermistors NTC/PTC, strain gauges): Commonly used bridge circuits or voltage divider circuits, require excitation voltage/current.
Voltage/Current Types: May require amplification, filtering, level shifting.
Digital Interfaces (I2C, SPI, UART, 1-Wire): Understand basic protocol concepts (master/slave, clock, data lines), level shifting requirements (3.3V vs 5V).
4.4 Communication Interface Levels:
TTL: 5V (Vih~2V, Vil~0.8V), common in older devices.
CMOS: Wide voltage (e.g., 3.3V, 5V), Vih ≈ 0.7Vcc, Vil ≈ 0.3Vcc. High input impedance.
RS232: ±3V to ±15V, negative logic, requires level shifting chips (e.g., MAX232).
RS485/RS422: Differential signals, strong anti-interference, requires dedicated transceiver chips. Understand the role of termination resistors.
Level Shifting: Why is it needed? Common methods (dedicated level shifting chips, voltage divider resistors, MOSFET bidirectional converters).
END
Source:Big Fish Robotics
Copyright belongs to the original author. If there is any infringement, please contact for deletion..▍Recommended ReadingHow much does a genuine Keil cost?Microcontrollers can output PWM like thisSharing an embedded development debugging tool!→ Follow for more updates ←