Do you know how to use triode in circuits?

Transistors have two working states: static and dynamic. The DC working state of the triode when no signal is added is called static. At this time, the current in each pole is called static current. The working current after adding AC signal to the triode is called dynamic operating current. At this time, the triode is in the AC working state, that is, dynamic.

A complete transistor circuit analysis has four steps: DC circuit analysis, AC circuit analysis, component and repair diagram identification.

1. DC circuit analysis method

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

Through this step of analysis, we can figure 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 amplifier DC circuit analysis. For a single-stage amplifier, its DC circuit analysis mainly includes the three parts shown in the figure.

When analyzing a transistor DC circuit, since the capacitors in the circuit have DC blocking characteristics, they can be regarded as open circuits. In this way, the circuit shown in the above figure can be drawn as a DC equivalent circuit as shown in the figure below, and then use this equivalent circuit. DC circuit analysis of the circuit is quite simple.

2. AC circuit analysis method

AC circuit analysis is mainly the analysis of the transmission route of the AC signal, that is, where the signal is input into the amplifier, what 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 AC signal transmission route analysis.

In addition, it is necessary to analyze what processing the signal has received during the transmission process, such as which link the signal is amplified, which link it is attenuated, which link it does not amplify or attenuate, whether the signal is compensated, etc.

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

3. Component function analysis method

3.1 Component characteristics are key to circuit analysis

When analyzing the role of components in a circuit, it should be based on the main characteristics of the component. For example, a coupling capacitor allows AC signals to pass without loss while blocking the DC path. The theoretical basis for this analysis is the DC and AC blocking characteristics of the capacitor.

3.2 The specific role of components in the circuit

Each component in the circuit has its specific role. Usually one component plays one specific role. Of course, there are also components that play two roles in the circuit. In circuit analysis, it is required to understand the specific role of each component in the circuit.

3.3 Simplified analysis method of components

The analysis of the role of components can be simplified. After mastering the role of components in the circuit, it is not necessary to conduct detailed analysis of each component every time. For example, after understanding 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.

4. Repair diagram identification method

Repair diagram identification is a service for troubleshooting circuit faults. This diagram identification requires a complete understanding of the working principle of the circuit, otherwise it is meaningless. Because the fault phenomenon is clear, the repair diagrams during the troubleshooting process can be carried out by selecting the components in the circuit in a targeted manner, without the need to perform fault analysis on each component in the circuit.

During analysis, find out the main components in the circuit and assume that they have faults such as open circuit, short circuit, increased or decreased resistance, analyze the impact of such faults on DC circuits and AC circuits, and deduce the possible root causes of the faults. 

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

4.1 Key test points of single-stage amplifier

As shown in the figure, the single-stage amplifier is mainly the critical test point of the triode.

The key test points of the transistor are used to measure the DC working voltage of the three electrodes. The collector is the first test point, followed by the base and the third is the emitter.

4.2 Key test points of integrated circuits

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

5. Transistor base bias circuit analysis method

The analysis of the base bias circuit of a triode is the most difficult. Mastering some circuit analysis methods can facilitate the analysis of the base bias circuit.

5.1 The first step in circuit analysis is to find the circuit symbol of the triode in the circuit, as shown in the figure, and then find the base in the triode circuit symbol. This is a key step in analyzing the base bias circuit.

5.2 The second step starts from the base and finds all the components connected to the base and the power terminal. As shown in the figure, RB1 in the circuit, and then finds all the components connected to the base and the ground. Such as RB2 in the circuit, these components form the main circuit of the base bias circuit.

After the Dyethin test and analysis of the above components connected to the base, it is necessary to distinguish which components may be components in the bias circuit. The resistor may form a bias circuit, and the capacitor has a DC blocking effect and is considered an open circuit. Therefore, when analyzing the base DC bias circuit, the capacitor does not need to be considered.

3. In the third step, after determining the components in the bias circuit, analyze the base current loop, as shown in the figure. The base current loop is: DC operating voltage VCC→bias resistor RB1→VT1 base→VT1 emitter→VT1 emitter resistor RE→ground.

6.Parameter explanation of triode

△ λ---Spectral half-width

△VF---Forward voltage drop difference

△Vz---voltage increment of voltage regulation range

av---voltage temperature coefficient

a---temperature coefficient

BV cer---base and emitter are connected in series with a resistor, CE junction breakdown voltage

BVcbo---emitter open circuit, breakdown voltage between collector and base

BVceo---base open circuit, CE junction breakdown voltage

BVces---Base and emitter short circuit CE junction breakdown voltage

BVebo---open collector EB junction breakdown voltage

Cib --- common base input capacitor

Cic---collector junction barrier capacitance

Cieo---common emitter open input capacitor

Cies---common emitter short circuit input capacitor

Cie --- common emitter input capacitance

Cjo/Cjn---junction capacitance change

Cjo---zero bias junction capacitance

Cjv---bias junction capacitance

Cj---junction (interelectrode) capacitance, indicating the total capacitance of the germanium detection diode under the specified bias voltage applied to both ends of the diode.

CL---load capacitance (external circuit parameters)

Cn---neutralizing capacitor (external circuit parameters)

Cob---common base output capacitor. In the base circuit, the output capacitance between the collector and the base

Coeo---common emitter open circuit output capacitor

Coe---common emitter output capacitance

Co---zero bias capacitor

Co---output capacitor

Cp---parallel capacitance (external circuit parameters)

Cre---common emitter feedback capacitor

Cs---case capacitor or package capacitor

CTC---capacitance temperature coefficient

CTV---voltage temperature coefficient. The ratio of the relative change of the stable voltage to the absolute change of the ambient temperature under the test current

Ct---total capacitance

Cvn---nominal capacitance

di/dt---critical rise rate of on-state current

dv/dt---critical rise rate of on-state voltage

D---duty cycle

ESB---secondary breakdown energy

fmax---the highest oscillation frequency. The operating frequency when the transistor power gain is equal to 1

fT---Characteristic frequency

f---frequency

h RE---common emitter static voltage feedback coefficient

hFE---common emitter quiescent current amplification factor

hfe---minimum signal total emission short-circuit voltage amplification factor

hIE---common emitter static input impedance

hie --- total emission of very small signal short circuit input impedance

hOE---common emitter static output conductance

hoe --- total emission of very small signal open circuit output admittance

hre---Total very small signal open circuit voltage feedback coefficient

IAGC---forward automatic control current

IB2---Base modulation current in unijunction transistor

IBM---the maximum value of DC current that can continuously pass through the base within the range of the collector's allowed power dissipation, or the maximum average value of AC current

IB---the average value of base DC current or AC current

Icbo---the base is grounded, the emitter is open to ground, the reverse cut-off current between the collector and the base under the specified VCB reverse voltage condition

Iceo---the emitter is grounded, the base is open to ground, and under the specified reverse voltage VCE condition, the reverse cut-off current between the collector and the emitter

Icer---a series resistor R between the base and the emitter. When the voltage VCE between the collector and the emitter is a specified value, the reverse cut-off current between the collector and the emitter is

Ices---the emitter is grounded, the base is short-circuited to ground, and under the specified reverse voltage VCE condition, the reverse cut-off current between the collector and the emitter

Icex---The emitter is grounded, a specified bias voltage is applied between the base and the emitter, and under the specified reverse bias voltage VCE, the reverse cut-off current between the collector and the emitter

ICMP---collector maximum allowable pulse current

ICM---the maximum allowable current of the collector or the maximum average value of the AC current.

ICM---Maximum output average current

Ic---the average value of collector DC current or AC current

IDR---Thyristor off-state average repetitive current

ID---dark current

IEB10---Reverse current between the emitter and the first base in a double-base unijunction transistor

IEB20---emitter current in double base unijunction transistor

Iebo---the base is grounded, the collector is open to ground, and under the specified reverse voltage VEB condition, the reverse cut-off current between the emitter and the base

IEM---emitter peak current

IE---the average value of emitter DC current or AC current

IF(AV)---forward average current

IF(ov)---Forward overload current

IFM (IM)---Forward peak current (forward maximum current). The maximum forward pulse current allowed through the diode at rated power. LED limiting current.

IFMP---forward pulse current

IFRM---forward repetitive peak current

IFSM---forward non-repetitive peak current (surge current)

IF---Forward DC current (forward test current). The current passing through the inter-electrode of the germanium detection diode under the specified forward voltage VF; the maximum operating current (average value) allowed to pass continuously in the sinusoidal half-wave of the silicon rectifier and silicon stack under the specified conditions of use, and the silicon switch The maximum forward DC current allowed to pass through the diode under rated power; the current given when measuring the forward electrical parameters of the Zener diode

iF---forward total instantaneous current

IGD---Thyristor control pole does not trigger current

IGFM---control electrode forward peak current

IGT---Thyristor control electrode trigger current

IH---Constant current, holding current.

Ii---light-emitting diode ignition current

IL---photocurrent or steady current diode limit current

IOM---maximum forward (rectified) current. Under specified conditions, the maximum forward instantaneous current that can be withstood; the maximum operating current allowed to continuously pass through the germanium detector diode in a sinusoidal half-wave rectifier circuit with a resistive load

Iop---operating current

Io---rectified current. The operating current that passes under specified frequency and specified voltage conditions in a specific line

IP---peak current

IR(AV)---reverse average current

IR (In)---Reverse DC current (reverse leakage current). When measuring the reverse characteristics, a given reverse current; the current passing through when silicon is stacked in a sinusoidal half-wave resistive load circuit and a specified value of reverse voltage is applied; the reverse operating voltage VR is applied to both ends of the silicon switching diode The current passing through; the leakage current generated by the Zener diode under the reverse voltage; the leakage current of the rectifier under the highest reverse operating voltage of the sine half wave.

IRM---Inverse peak current

Irp---reverse recovery current

IRRM---inverse repetitive peak current

IRR---Thyristor reverse repetitive average current

IRSM---reverse non-repetitive peak current (reverse surge current)

ir---reverse recovery current

iR---reverse total instantaneous current

ISB---secondary breakdown current

Is---Stabilizing diode current stabilization

IV---valley point current

Izk---Knee point current of voltage regulator tube

IZM---Maximum regulated current. The current allowed to pass through the Zener diode at maximum power dissipation

IZSM --- Zener diode surge current

Iz --- Stable voltage and current (reverse test current). When testing reverse electrical parameters, the given reverse current

n---capacitance change index; capacitance ratio

PB---withstand pulse burnout power

PCM---the maximum allowable power dissipation of the collector

Pc---Collector dissipation power

PC---Control pole average power or collector dissipated power

Pd---dissipated power

PFT (AV)---average power dissipated in forward conduction

PFTM---forward peak power dissipation

PFT---Forward conduction total instantaneous power dissipation

PGM---peak gate power

PG---gate average power

Pi---input power

Pi---input power

PK---maximum switching power

PMP---maximum leaked pulse power

PMS---maximum withstand pulse power

PM---rated power. The maximum power that the silicon diode can withstand when its junction temperature is not higher than 150 degrees

Pn---noise power

Pomax---maximum output power

Posc---oscillation power

Po---output power

Po---output power

PR---reverse surge power

Psc---continuous output power

PSM---non-repetitive surge power

Ptot---total power dissipated

Ptot---total power dissipated

PZM---maximum power dissipation. The maximum power a Zener diode is allowed to withstand under given conditions of use

Q---Excellence value (quality factor)

r δ---attenuation resistance

R(th)ja----Thermal resistance from junction to environment

R(th)jc---Thermal resistance from junction to case

r(th)---Transient resistance

rbb minutes Cc---base-collector time constant, which is the product of base extension resistance and collector junction capacitance

rbb minutes---base area extended resistance (base area intrinsic resistance)

RBB---Resistance between bases of double-base transistor

RBE---external base-emitter resistance (external circuit parameters)

RB---external base resistor (external circuit parameters)

Rc ---External collector resistor (external circuit parameters)

RE---radio frequency resistor

RE---External emitter resistor (external circuit parameters)

RF(r)---Forward differential resistance. During forward conduction, the current shows obvious nonlinear characteristics as the voltage index increases. Under a certain forward voltage, if the voltage increases by a small amount △V, the forward current increases correspondingly by △I, then △V/△I is called differential resistance.

RG---signal source internal resistance

rie---the input resistance when the emitter is grounded and the AC output is short-circuited

RL---load resistance

RL---Load resistance (external circuit parameters)

roe---The output resistance when the emitter is grounded and the AC input is short-circuited when measured under specified VCE, Ic or IE, and frequency conditions.

Rs(rs)----series resistance

Rth---thermal resistance

Rth----Thermal resistance

Rz(ru)---Dynamic resistance

Ta---ambient temperature

Ta---ambient temperature

Tc---tube shell temperature

Tc---case temperature

td---delay time

td----delay time

tfr---forward recovery time

tf---fall time

tf---fall time

tgt---gate control pole turn-on time

tg---circuit commutation off time

Tjm---maximum allowable junction temperature

Tjm---maximum junction temperature

Tj---junction temperature

toff---off time

toff---off time

ton---opening time

ton---opening time

trr---reverse recovery time

tr---rise time

tr---rise time

tstg---storage temperature of temperature compensation diode

Tstg---storage temperature

ts---storage time

ts---storage time

Ts---junction temperature

V n---noise voltage

V v---Valley point voltage

V(BR)---breakdown voltage

VAGC---forward automatic gain control voltage

VB2B1---voltage between bases

VBB---base (DC) power supply voltage (external circuit parameters)

VBE(sat)---the emitter is grounded, and under specified Ic and IB conditions, the base-emitter saturation voltage drop (forward voltage drop)

VBE10---reverse voltage between emitter and first base

VBE---base-emitter (DC) voltage

VB---reverse peak breakdown voltage

VCBO---the base is grounded, the emitter is open to ground, and the maximum withstand voltage between the collector and the base under specified conditions

VCB---collector-base (DC) voltage

Vcc---Collector (DC) power supply voltage (external circuit parameters)

VCE(sat)---the emitter is grounded, and the saturation voltage drop between the collector and the emitter is specified under Ic and IB conditions.

VCEO---The emitter is grounded, the base is open to ground, and the maximum withstand voltage between the collector and emitter under specified conditions

VCER---The emitter is grounded, a resistor R is connected in series between the base and the emitter, and the maximum withstand voltage between the collector and the emitter under specified conditions

VCES---the emitter is grounded, the base is short-circuited to ground, the maximum withstand voltage between the collector and the emitter under specified conditions

VCEX---The emitter is grounded, a specified bias voltage is applied between the base and the emitter, and the maximum withstand voltage between the collector and the emitter under specified conditions

VCE---collector-emitter (DC) voltage

Vc---rectified input voltage

VDRM---off-state repetitive peak voltage

VEBO---the base is grounded, the collector is open to ground, and the maximum withstand voltage between the emitter and the base under specified conditions

VEB---saturation voltage drop

VEE---Emitter (DC) power supply voltage (external circuit parameters)

VF(AV)---forward average voltage

VFM---maximum forward voltage drop (forward peak voltage)

VF---Forward voltage drop (forward DC voltage)

VGD---gate non-trigger voltage

VGFM---gate forward peak voltage

VGRM---gate reverse peak voltage

VGT---gate trigger voltage

Vk---Knee point voltage (stabilizing diode)

VL ---limit voltage

Vn(p-p)---peak value of equivalent noise voltage at input end

Vn---center voltage

VOM---maximum output average voltage

Vop---working voltage

Vo---AC input voltage

Vp---Punch-through voltage.

Vp---peak voltage

VRM---reverse peak voltage (highest test voltage)

VRRM---reverse repetitive peak voltage (reverse surge voltage)

VRWM---reverse working peak voltage

VR---reverse operating voltage (reverse DC voltage)

VSB---secondary breakdown voltage

Vs---lead voltage (signal voltage) or current regulator stabilized current voltage

Vth---valve voltage (threshold voltage)

Vz---stable voltage

δvz---voltage regulator tube voltage drift

eta---single-junction transistor partial pressure ratio or efficiency

λp---luminescence peak wavelength