Four-Step Analysis Method of Triode Circuit 2022

Author: Release time:2022-10-26 Source: Font: Big Middle Small View count:218

We all know that the triode has two working states, static and dynamic. When no signal is applied, the DC working state of the transistor is called static state, and the current of each pole is called static current.

 

The working current after adding AC signal to the transistor is called dynamic working current. At this time, the transistor is in the AC working state, that is, dynamic.

 

Ⅰ. Introduction to Triode


Triode, the full name should be semiconductor triode, also known as bipolar transistor, is a semiconductor device that controls current. The function of it is to amplify the weak signal into an electrical signal with a larger amplitude value.

 

The triode is one of the basic components of semiconductors, which has the function of current amplification and is the core component of electronic circuits. Both PN joints split the entire semiconductor right into three parts. The middle part is the base location, as well as both sides are the emitter location and also the collection agency location. The arrangement is PNP and NPN.

 

The Application of Triode


Triodes tubes are typically made use of on sound and also superhigh frequency as an amplifier detector and also oscillator. Nonetheless, two defects are discovered in the use of triode, the initial issue being that its plate current partially depends on grid voltage as well as partially on plate voltage.

 

Ⅱ. Four-step analysis method of triode circuit


A complete triode circuit analysis has four steps: DC circuit analysis, AC circuit analysis, components and repair map.

 

2.1. DC circuit analysis method

 

The DC working voltage is applied to each electrode of the triode mainly through two DC circuits: one is the DC circuit between the collector and the emitter of the triode, and the other is the base DC circuit.

 

Through this step of analysis, it is possible to find out how the DC operating voltage is applied to the collector, base and emitter. As shown in the figure, it is a schematic diagram of the DC circuit analysis of the amplifier. For a single-stage amplifier, its DC circuit analysis is mainly the three parts shown in the figure.

 

dc circuit analysis method1.png


When analyzing the DC circuit of the triode, since the capacitors in the circuit have DC blocking characteristics, they can be regarded as open circuits, so that the circuit shown in the above figure can be drawn as the DC equivalent circuit shown in the figure below, and then use this equivalent Circuit analysis of DC circuits is quite straightforward.

 

2.2. AC circuit analysis method

 

The AC circuit analysis is mainly the analysis of the transmission route of the AC signal, that is, where the signal is input to the amplifier, which components the signal passes through in this amplifier, and where the signal is finally output. As shown in the figure, it is a schematic diagram of the analysis of the AC signal transmission route.

 

ac circuit analysis method.jpg

 

In addition, it is necessary to analyze the processing of the signal during the transmission process, such as which part of the signal is amplified, which part is attenuated, which part is neither amplified nor attenuated, whether the signal is compensated, etc.

 

The signal in the circuit in the figure above passes through C1, VT1, C2, VT2 and C3, of which C1, C2 and C3 are coupling capacitors, which do not amplify and attenuate the signal, but only play a coupling role in transmitting the signal to the lower-level circuit. VT1 and VT2 amplify the signal.

 

2.3. Analysis method of component function

 

1. Component characteristics are the key to circuit analysis

 

When analyzing the function of a component in a circuit, it should be carried out according to the main characteristics of the component. For example, the coupling capacitor allows the AC signal to pass through without loss, while blocking the DC path at the same time. The theoretical basis of this analysis is the DC blocking characteristic of the capacitor.

 

2. The specific role of components in the circuit

 

Each component in the circuit has its specific role, usually a component plays a specific role, of course, there is also a component that plays two roles in the circuit. In circuit analysis, it is required to understand the specific role of each component in the circuit.

 

3. Simplified analysis method of components

 

The analysis of the function of components can be simplified. After mastering the function of components in the circuit, it is not necessary to analyze each component in detail every time. For example, once you have a grasp of the role of coupling capacitors, it is not necessary to analyze every coupling capacitor. As shown in the figure, it is a schematic diagram of coupling capacitance analysis.

 

analysis method of component function.jpg

 

4.  The repair method

 

The repair map is a service for repairing circuit faults. This map requires that you fully understand the working principle of the circuit, otherwise it is meaningless. Because the fault phenomenon is clear, the repair identification map in the troubleshooting process can be carried out by selecting the components in the circuit in a targeted manner, and it is not necessary to check the fault of each component in the circuit.

 

When analyzing, find out the main components in the circuit, and assume that they have faults such as open circuit, short circuit, resistance value increase and decrease, analyze the impact of such faults on DC circuits and AC circuits, and infer the possible source of the fault. .

 

The key to repairing the picture is to find the key test points in the circuit:

 

1. Key test points for single-stage amplifiers

 

As shown, the single-stage amplifier is primarily a critical test point for triodes.

 

the repair method.jpg

 

The key test point of the triode is used to measure the DC working voltage of the three electrodes, of which the collector is the first test point, the second is the base, and the third is the emitter.

 

2. Key test points of integrated circuits

 

The most important test points for integrated circuits are the power supply pins, as well as input signal pins and output signal pins.

 

 

Ⅲ. The distinction between a triode and also a diode


3.1. Basic difference between triode and diode


The fundamental difference between diodes and also triodes is that diode has 2 feet, triode three feet, triode has the duty of present amplification (i.e., the base present on the enthusiast current control role.) Diode does not have boosting, it has a one-way conductive residential or commercial properties.

 

Amplification: is the base current on the collection agency present control duty, revealed as: the base current change, mirrored in the collection agency is a symmetrical (collection agency current = base existing increased by the boosting of the transistor) of the present modification.

 

The significance of boosting is with the transistor's present control function, from the power supply to obtain power, the base input analog boosting output in the collection agency tons (the adjustment in existing, in the tons and also shared as an adjustment in voltage). Therefore, what is in fact amplified is the analog quantity of the base input.

 

3.2. Distinction in working principle between triode and diode


A diode is a two-terminal tool with unidirectional transmission. It is split into digital diodes and crystal diodes. Electronic diodes are rarely seen currently, and also a lot of the a lot more usual and also commonly utilized are crystal diodes.

 

The unidirectional conduction features of diodes are utilized in almost all digital circuits. Semiconductor diodes is important in many circuits. It is just one of the earliest semiconductor tools, as well as its application is additionally extremely commonly.

 

The working concept of the triode

 

The triode is a control part to control the dimension of the existing. Take the common-emitter link as an example (the signal is input from the base, result from the collector, and also the emitter is based). When the base voltage UB has a minor modification, the base current IB will certainly likewise have a small change. Under the control of the base present IB, the enthusiast present IC will have a big modification.

 

The bigger the base existing IB, the larger the collector existing IC. On the other hand, the smaller sized the base current is, the smaller the collection agency current is, that is, the base existing controls the adjustment of the enthusiast present. But the modification of collector existing is much larger than the change of base current, which is the amplification result of triode.

 

The ratio of the modification of IC to the adjustment of IB is called the magnifying β of the triode (β=ΔIC/ ΔIB, Δ stands for the adjustment.) The magnification β of the triode is usually 10s to hundreds of times.

When the triode is enhancing the signal, it needs to initially get in the conducting state, that is, it should initially develop an appropriate fixed operating point, also referred to as establishing a prejudice, or else it will magnify as well as distort.

 

The diode is primarily unidirectional conductivity, and also the triode is generally the boosting of voltage and also current.


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