Understand 20 types of analog circuits in one article

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Understand 20 types of analog circuits in one article [Copy link]

The primary level is to memorize these 20 circuits skillfully and understand their functions. Anyone who studies automation, electronics and other electronic control majors should and can memorize these 20 basic analog circuits.

The intermediate level is to be able to analyze the role of the key components in these twenty circuits, the impact of each component failure on the circuit function, the change rules of parameters during measurement, and master the treatment methods for faulty components; qualitatively analyze the flow direction and phase change of circuit signals; qualitatively analyze the change process of signal waveforms; qualitatively understand the size of circuit input and output impedance, and the relationship between signal and impedance. With this circuit knowledge, you are very likely to grow into an excellent maintenance technician for electronic products and industrial control equipment.

The advanced level is to be able to quantitatively calculate the input and output impedance of these twenty circuits, the ratio of output signal to input signal, the relationship between the signal current or voltage in the circuit and the circuit parameters, the relationship between the amplitude and frequency of the signal in the circuit, the relationship between the phase and frequency, the selection of component parameters in the circuit, etc. After reaching the advanced level, as long as you are willing, the respected and high-paying career - development and design engineer of electronic products and industrial control equipment will be your first choice.

01

Bridge rectifier circuit

Points to note:

1. Unidirectional conductivity of diode:

When a forward voltage is applied to the PN junction of a diode, it is in the on state; when a reverse voltage is applied, it is in the off state.

Volt-ampere characteristic curve:

Ideal switch model and constant voltage drop model:

The ideal model means that when the diode is forward biased, its tube voltage drop is 0, and when it is reverse biased, its resistance is infinite and the current is zero, which means it is cut off. The constant voltage drop model means that when the diode is turned on, its tube voltage drop is a constant value, 0.7V for silicon tubes and 0.5V for germanium tubes.

2. Bridge rectifier current flow process:

When u2 is in the positive half cycle, diodes Vd1 and Vd2 are turned on; while multipolar transistors Vd3 and Vd4 are turned off, the current on the load RL flows through the load from top to bottom, and the load obtains the same voltage as the positive half cycle of u2; in the negative half cycle of u2, the actual polarity of u2 is positive at the bottom and negative at the top, diodes Vd3 and Vd4 are turned on while Vd1 and Vd2 are turned off, and the current on the load RL still flows through the load from top to bottom, and the load obtains the same voltage as the positive half cycle of u2.

3. Calculation:

Vo, Io, diode reverse voltage:

Uo=0.9U2, Io=0.9U 2/RL,URM=√2 U 2

02

Power filter

Points to note:

1. Process analysis of power supply filtering:

Power supply filtering is to connect a large-capacity capacitor in parallel across the load RL. Since the voltage across the capacitor cannot change suddenly, the voltage across the load will not change suddenly either, so the output voltage can be smoothed to achieve the purpose of filtering.

Waveform formation process:

When the output terminal is connected to the load RL, when the power supply is powered, the current is provided to the load and the capacitor C is charged at the same time. The charging time constant is τcharging = (Ri∥RLC) ≈ RiC. Generally, Ri〈〈RL. Ignoring the influence of Ri voltage drop, the voltage on the capacitor will rise rapidly with u2. When ωt=ωt1, u2=u0. After that, u2 is lower than u0. All diodes are cut off. At this time, the capacitor C discharges through RL. The discharge time constant is RLC, the discharge time is slow, and u0 changes smoothly. When ωt=ωt2, u2=u0. After ωt2, u2 changes to be larger than u0 again, and the charging process begins again. u0 rises rapidly. When ωt=ωt3, u2=u0. After ωt3, the capacitor discharges through RL. This is repeated, and the charging and discharging are repeated periodically. Due to the energy storage effect of capacitor C, the voltage fluctuation on RL is greatly reduced. Capacitor filtering is suitable for occasions where the current does not change much. LC filtering circuit is suitable for occasions where the current is large and the voltage pulsation is required to be small.

2. Calculation:

Selection of filter capacitor capacity and withstand voltage

The output voltage Uo of the capacitor filter rectifier circuit is between √2U 2 and 0.9U 2, and the average value of the output voltage depends on the size of the discharge time constant.

Capacitor capacity RLC ≧ (3~5) T/2, where T is the period of the AC power supply voltage. In practice, it is often further approximated as Uo≈1.2U2, the maximum reverse peak voltage of the rectifier URM=√2U 2, and the average current of each diode is half of the load current.

03

Signal filter

Points to note:

1. The function of signal filter:

Attenuate the unwanted signal components in the input signal to a sufficiently small level, but at the same time allow the useful signal to pass smoothly.

Differences and similarities with power supply filters:

The difference between the two is: the signal filter is used to filter the signal, and its passband is a certain frequency range, while the power supply filter is used to filter out the AC component and allow the DC to pass, thereby keeping the output voltage stable; the AC power supply only allows a specific frequency to pass.

Similarities: Both work using the amplitude-frequency characteristics of the circuit.

2. Impedance calculation of LC series and parallel circuits:

When connected in series, the circuit impedance is Z=R+j(XL-XC)=R+j(ωL-1/ωC);

When connected in parallel, the circuit impedance is Z=1/jωC∥(R+jωL)=

Considering that in practice, R<<ωL is often the case, so Z≈

Amplitude-frequency relationship and phase-frequency relationship curves:

3. Plot the passband curve:

Calculate the resonant frequency: fo=1/2π√LC

04

Differentiation and integration circuits

Points to note:

1. The function of the circuit, the difference and similarity with the filter;

2. Analyze the voltage change process of differential and integral circuits and draw the voltage change waveform;

3. Calculation: time constant, voltage change equation, selection of resistance and capacitance parameters.

05

Common emitter amplifier circuit

Points to note:

1. The structure of the transistor, the relationship between the currents of each pole of the transistor, the characteristic curve, and the amplification conditions;

2. The functions of components, the purpose of circuits, voltage amplification, the phase relationship of input and output signal voltages, and AC and DC equivalent circuit diagrams;

3. Calculation of static operating point and voltage amplification factor.

06

Voltage-divided bias common emitter amplifier circuit

Points to note:

1. The functions of components, the purpose of circuits, voltage amplification, the phase relationship of input and output signal voltages, and AC and DC equivalent circuit diagrams;

2. Analysis of the current series negative feedback process and the impact of negative feedback on circuit parameters;

3. Calculation of static operating point and voltage amplification factor;

4. Analysis of controlled source equivalent circuit.

07

Common collector amplifier circuit (emitter follower)

Points to note:

1. The function of components, the purpose of circuits, voltage amplification, the phase relationship of input and output signal voltages, AC and DC equivalent circuit diagrams, and the input and output impedance characteristics of circuits;

2. Analysis of the current series negative feedback process and the impact of negative feedback on circuit parameters;

3. Calculation of static operating point and voltage amplification factor.

08

Circuit Feedback Block Diagram

Points to note:

1. The concept of feedback, positive and negative feedback and their judgment methods, parallel feedback and series feedback and their judgment methods, current feedback and voltage feedback and their judgment methods;

2. Amplification gain with negative feedback circuit;

3. The influence of negative feedback on the circuit's amplification gain, passband, gain stability, distortion, input and output resistance.

09

Diode voltage regulator circuit

Points to note:

1. Characteristic curve of Zener diode;

2. Notes on the application of Zener diodes;

3. Analysis of voltage stabilization process.

10

Series regulated power supply

Points to note:

1. The block diagram of the series voltage-stabilized power supply;

2. The function of each component; voltage stabilization process analysis;

3. Calculate output voltage.

11

Differential amplifier circuit

Points to note:

1. The functions of each component of the circuit, the purpose of the circuit, and the characteristics of the circuit;

2. Analysis of the working principle of the circuit. How to amplify the differential mode signal and suppress the common mode signal;

3. The circuit's single-ended input and double-ended input, single-ended output and double-ended output working modes.

12

Field effect tube amplifier circuit

Points to note:

1. Classification, characteristics, structure, transfer characteristics and output characteristic curve of field effect tubes;

2. Characteristics of field effect amplifier circuit;

3. Application scenarios of field effect amplifier circuits.

13

Frequency selective (bandpass) amplifier circuit

Points to note:

1. The function of each component, the characteristics of the frequency selective amplifier circuit, and the function of the circuit;

2. Calculation of characteristic frequency and selection of frequency selection component parameters;

3. Amplitude-frequency characteristic curve.

14

Operational amplifier circuit

Points to note:

1. The concept of an ideal operational amplifier, a virtual short circuit at the input of the operational amplifier, and a virtual open circuit at the input of the operational amplifier;

2. The main purpose of the op amp circuit with inverting input mode, the phase relationship between the input voltage and the output voltage signal;

3. Gain expression, input impedance, and output impedance under the same-phase input mode.

15

Differential Input Operational Amplifier Circuit

Points to note:

1. Characteristics and uses of differential input operational amplifier circuit;

2. The relationship between output signal voltage and input signal voltage.

16

Voltage Comparator Circuit

Points to note:

1. The function and working process of voltage comparator;

2. Input-output characteristic curve of the comparator;

3. How to construct a hysteresis comparator.

17

RC Oscillator Circuit

Points to note:

1. The composition, function, phase conditions for oscillation, and amplitude conditions for oscillation and balance of the oscillation circuit;

2. The relationship curve between RC circuit impedance and frequency, and the relationship curve between phase and frequency;

3. Analysis of phase conditions of RC oscillation circuit, oscillation frequency, and how to select components.

18

LC Oscillator Circuit

Points to note:

1. Analysis of oscillation phase conditions;

2. DC equivalent circuit diagram and AC equivalent circuit diagram;

3. Calculation of oscillation frequency.

19

Quartz crystal oscillator circuit

Points to note:

1. Characteristics of quartz crystal, equivalent circuit of quartz crystal, characteristic curve of quartz crystal;

2. Characteristics of quartz crystal oscillator;

3. The oscillation frequency of the quartz crystal oscillator.

20

Power amplifier circuit

Points to note:

1. The working process and crossover distortion of Class B power amplifier;

2. Compound rules of compound triode;

3. Working principle of Class AB power amplifier, bootstrap process, Class A power amplifier, characteristics of Class AB power amplifier.

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Jacktang

In the signal filter circuit, it is rare to connect the inductor in a circle like this.

freebsder

If you can understand this, you don't need to spend a year studying circuit simulation in college. . .

se7ens

The final power amplifier circuit has high static power consumption

The static working point needs to be adjusted when using

Otherwise it is easy to be distorted

EDSGVD

XUEXIXUEXI

well_kim