[introduction] diode divides one-way electric conduction outside character, still have a lot of character, not be to use one-way and electric character to be able to analyse diode place to constitute the working principle of circuit in very much circuit, and more characteristic ability analyse need control diode correctly these circuit, for example the circuit of stabilized voltage of simple and easy dc that diode makes, the temperature that diode forms compensates circuit to wait.

A lot of abecedarian are right diode very ” familiar ” , mention the one-way electric conduction that the character of diode can blurt out it is characteristic, respecting its applied reaction in circuit is rectification, not much to the other character of diode and applied understanding, the one-way electric conduction that also thought to master diode on understanding is characteristic, with respect to all sorts of circuit that can analyse diode to participate in, actually such idea is wrong, and going up somehow was to kill his, because this kind of directional thinking was affected,work to all sorts of diode circuit the analysis of the principle, a lot of diode circuit cannot use one-way and electric character to explain its work principle.

Diode divides one-way electric conduction outside character, still have a lot of character, not be to use one-way and electric character to be able to analyse diode place to constitute the working principle of circuit in very much circuit, and more characteristic ability analyse need control diode correctly these circuit, for example the circuit of stabilized voltage of simple and easy dc that diode makes, the temperature that diode forms compensates circuit to wait.

Circuit of stabilized voltage of simple and easy dc and breakdown handle 01 diode

Circuit of simple and easy stabilized voltage basically uses diode in circuit of a few local volts d.c. supply, because circuit is simple, cost is low, application is so wider.

The pipe that diode basically uses diode in circuit of simple and easy stabilized voltage is pressed fall basic and changeless character.

The canal of diode presses fall characteristic: Diode guides after connecting, its canal is pressed fall basic and changeless, this one canal controls to silicon detector speech falling is 0.6V left and right sides, to germanium diode character is 0.2V left and right sides.

If plan institute is shown,be by common the circuit of stabilized voltage of simple and easy dc that 3 diode make. The VD1 in circuit, VD2 and VD3 are common diode, circuit of stabilized voltage of a simple and easy volts d.c. is made after their series connection rises.

1. Circuit analyses specification of train of thought

Analysing to never have the circuit job principle that has seen is difficult, not comprehensive to ABC abecedarian more difficult.

About the analysis of this one circuit train of thought basically explains as follows.

(1) can see from inside circuit 3 diode establish ties, according to series circuit character knowable, if these 3 diode guide a meeting guide at the same time, if end,can end at the same time.

(2) whether to guide according to diode the judgement principle that understand is analysed, receive in the anode of diode have get much tension higher than negative pole, no matter be the voltage of dc or communication, right now diode all is in on-state. Can see from inside circuit, the dc job voltage in circuit is being received through resistor R1 in VD1 anode + V, the negative pole ground connection of VD3, add on diode of 3 series connection so have enough big to volts d.c. . Analyse from this knowable, 3 diode VD1, VD2 and VD3 are shedding working voltage continuously + guide below V action those who connect.

(3) still can see from inside circuit, communication signal tension was not added on 3 diode, because be in,VD1 anode is received between the A dot in circuit and ground namely have C1 of high capacity capacitance, any alternating voltage bypass that nod A are carried to the ground.

2. Diode can stabilize specification of volts d.c. principle

In circuit, 3 diode are shedding working voltage continuously to slant guide below buy action, guide the to this one circuit action after connecting is the volts d.c. that the A in stabilizing circuit nods.

Well-known, diode interior is the structure that a PN writtens guarantee, PN knot still has a lot of character except one-way and electric character, among them one of it is diode guides after connecting, its canal is pressed fall basic and changeless, guide to commonly used silicon detector the voltage drop between the anode after connecting and negative pole is 0.6V.

According to this one character of diode, can very analyse the circuit of stabilized voltage of simple and easy dc that makes by common diode conveniently working principle. 3 diode guide after connecting, the canal of every diode is pressed falling is 0.6V, so the volts d.c. after 3 series connection falls is 0.6 × 3=1.8V.

3. Breakdown detects method

Detect 3 diode in this one circuit are effective method is the volts d.c. that measures diode to go up, if plan institute is shown,be sketch map of the wiring when measuring. If measure volts d.c. outcome,be 1.8V left and right sides, explain 3 diode job is regular; If measure volts d.c. outcome,be 0V, should measure dc job voltage + whether is V mixed normally resistor R1 whether open circuit, have nothing to do with 3 diode, because of 3 diode the possibility of puncture is lesser at the same time; If measure volts d.c. result to be more than 1.8V, the examination has trouble of an open a way in 3 diode.

4. Circuit breakdown is analysed

Be like watch place to show is this analysis of breakdown of one diode circuit

5. Circuit analyses detail specification

About afore-mentioned diode circuit of stabilized voltage of simple and easy volts d.c. analyses detail to explain as follows.

(1) in circuit analysis, the one-way conductivity that uses diode can know diode is in on-state, but can not explain these a few diode guide what there is to circuit after connecting specific action, use one-way and electric character to still cannot analyse circuit job principle quite correctly only so.

(2) diode guides the canal after connecting is pressed only in numerous character fall basic and changeless this one character can be a pragmatize the action of this one circuit, the dc job voltage that can decide according to this this one circuit is to stabilize the A in circuit to nod so.

(3) there are many in circuit yuan when parts of an apparatus, what must try to make clear Chu Shi shows circuit function is main yuan of parts of an apparatus, undertake spreading out an analysis around it next. Major attribute of this yuan of parts of an apparatus is used in the analysis, have logical explanation.

02 diode temperature compensates circuit and breakdown processing

Well-known, PN knot guides there is to be 0.6V about after connecting (PN of material pointing to silicon writtens guarantee) pressure fall, at the same time PN knot still has a character related to temperature: PN knot guides after connecting pressure fall basic and changeless, but not be changeless, PN writtens guarantee of two end pressure fall to lift along with temperature and drop somewhat, temperature heals tall the quantity that its drop heals much, of course PN writtens guarantee two upright voltage drop the to 0.6V talk of the quantity is quite small, use this one character to be able to form temperature to compensate circuit. If plan institute is shown,be the temperature compensation circuit that uses diode temperature character to form.

Will tell to abecedarian, seeing those who form do not know the VT1 in circuit to wait for yuan of parts of an apparatus is a kind of amplifier, this works to analysing this one circuit the principle is adverse. In circuit analysis, the unit circuit function that is familiar with VT1 to wait for place of yuan of parts of an apparatus to form, to analysing VD1 working principle is having active sense. Understood the function of unit circuit, all circuit analysises can undertake spreading out around it, accomplish have a definite object in view, get twice the result with half the effort.

1. The principle of job of circuit of deep administrative levels that needs knowledge

Analyse principle of job of this one circuit to need understanding to fall list two depth second circuit principle.

(1) VT1 make circuit of a kind of amplifier, ask to amplifier its working stability is good, the static electric current that having among them is the dynatron when temperature discretion changes is unalterable, VT1 base electric current cannot change along with temperature and change namely, work namely otherwise stability is bad. This one temperature that understands amplifier is characteristic, it is very important that the temperature that forms to understanding VD1 compensates circuit job principle.

(2) dynatron VT1 has an undesirable character related to temperature, namely when temperature is elevatory, electric current of dynatron VT1 base can increase, temperature heals tall base electric current heals big, conversely small, the temperature stability of apparent dynatron VT1 can be bad. From this knowable, the temperature stability of amplifier can be undesirable because dynatron temperature character is caused,be.

2. Dynatron slants buy circuit analysis

In circuit, dynatron VT1 job should give it certain dc bias voltage when enlarge condition, this by slant buy circuit will finish. The R1 in circuit, VD1 and R2 compose composition press type to slant buy circuit, offer dc job voltage for dynatron VT1 base, the size of base voltage decided the size of VT1 base electric current. If take no account of the influence of temperature, and dc job voltage + the size of V is changeless, so VT1 base volts d.c. is stability, criterion the base dc electric current of dynatron VT1 is changeless, dynatron can stabilize the job.

It is a bit clearer to do even when analysing principle of diode VD1 job: VT1 is NPN dynatron, its base volts d.c. is tall, criterion base electric current is big; Conversely small.

3. Diode VD1 temperature compensates circuit analysis

Be in according to diode VD1 the position in circuit, to its working principle analytic train of thought basically explains a few following:

(1) the anode of VD1 passes R1 and dc job voltage + V is linked together, and its negative pole is linked together through R2 and ground wire, such VD1 are shedding working voltage continuously + on-state is in below the action of V. Understanding diode guides the point that understand is: Positive electrode electrify presses the voltage on prep above negative pole.

(2) the function that uses diode to guide there is canal of a 0.6V to press the VD1 in falling to explain circuit after connecting won’ts do, the dc job voltage that because pass the block that adjusts R1 and R2 to be worth size,can achieve VT1 base place to need, not was necessary to adjust volume of VT1 base voltage through stringing together diode VD1 at all.

(3) the pipe that uses diode is pressed fall temperature character can explain VD1 correctly the action in circuit. Hypothesis temperature is elevatory, according to dynatron character knowable, the base electric current of VT1 can increase a few. When temperature is elevatory, the canal of diode VD1 is pressed fall can drop a few, VD1 canal presses falling fall to bring about VT1 base voltage to drop a few, the result makes VT1 base electric current drops. By afore-mentioned analysises knowable, after joining diode VD1, original temperature is elevatory make VT1 base electric current increases, can make through VD1 circuit VT1 base electric current is reduced now a few, have the effect of electric current of base of stable dynatron VT1 so, so VD1 can have temperature compensatory effect.

(4) the temperature stability of dynatron can be undesirable in still behaving the process that drops for temperature. When thermal drop is small, electric current of dynatron VT1 base wants to reduce, this also is the performance with temperature can bad stability. After receiving diode VD1, when temperature drops, its canal is pressed fall to have a bit elevatory, make voltage of job of VT1 base dc elevatory, electric current of result VT1 base increases, when also can compensating dynatron VT1 temperature to drop so not stable.

4. Circuit analyses detail specification

The detail that circuit analyses explains as follows.

(1) in circuit analysis, if can apply the some character of yuan of parts of an apparatus to go,it is in the pragmatize the action in circuit, explaining circuit analysis is probable is correct. For example, in afore-mentioned circuit analysises, the temperature character talent that can use diode only is reasonable the action of the VD1 in explaining circuit.

(2) the temperature compensation of temperature compensation circuit is two-way, can compensate the instability that works as a result of the circuit that temperature lifts or be reduced and causes namely.

(3) when analytic temperature compensates circuit job principle, want hypothesis temperature lift or reduce variation, analyse the reaction process in circuit next, get accurate circuit feedback result. In actual circuit analysis, can set temperature to lift only undertake circuit compensatory is analysed, need not analyse case of compensatory of the circuit when thermal drop is small again, it is similar that because of thermal drop low circuit analyses train of thought, process, the each stage change that is circuit analysis only is adverse.

(4) in afore-mentioned circuit analysises, VT1 base and blast off extremely between PN writtens guarantee (emissive knot) temperature character and VD1 temperature character are similar, because they are the structure that PN writtens guarantee, temperature compensatory outcome is so better.

(5) the diode VD1 in afore-mentioned circuit, to dc job voltage + the size wave motion of V does not have stabilization, cannot compensate so by dc job voltage + the instability of the electric current of job of dc of VT1 canal base that V size wave motion causes.

5. Breakdown detects method and circuit breakdown analysis

The diode VD1 breakdown in this one circuit detects the method is simpler, can use avometer ohm archives to measure VD1 in the road to the method with retrorse resistor size.

When breakdown of VD1 occurrence open a way, bias voltage of dc of dynatron VT1 base is elevatory a lot of, bring about VT1 canal to enter saturated state, VT1 may have a fever, serious when can burned-out VT1. If VD1 appears puncture breakdown, can bring about VT1 to be in charge of base dc bias voltage to drop 0.6V, electric current of job of dynatron VT1 dc is reduced, VT1 canal magnifies ability is reduced or enter off-state.

03 diode control circuit and breakdown processing

Diode guides after connecting, its changing along with voltaic size to resistor size and have little change, healing to electric current big, healing to resistor small; Conversely big.

Use diode to electric current and to the character between resistor, can make circuit of a few automata. Be like graph 9-43 place to show is a kind of automata circuit that makes by diode, call ALC circuit again (automatic n dominates circuit) , it is in magnetic recording equipment (if get stuck) often apply in recording circuit.

1. Circuit analysis prepares intellectual specification

The character of only guide report of diode just explained to resistor small, retrorse resistance is great, without the specification diode guides there still is what particular character after connecting.

Diode after guide is connected, its returning to resistor size with what had shed diode to voltaic size relevant. Although diode is being compared after guide is connected to resistor small (relatively retrorse resistor) , but if increase to electric current, diode guides still can dropping after connecting further to resistor, healing to electric current namely big, healing to resistor small, conversely big.

Function of not familiar circuit is very adverse to circuit job principle, fall in the setting that understands circuit function can principle of job of circuit of analysis of ground of have a definite object in view or the action of some yuan of parts of an apparatus in circuit.

ALC circuit is in recorder, card in recording card, the volume range that pair of recording signal want when recording undertakes controlling, understanding issues an a few specific control to ask to conduce to circuit of automata of analytic diode VD1.

(1) when recording signal extent is lesser, do not control the extent of recording signal.

(2) arrive greatly when the extent of recording signal after certain level, begin to undertake controlling to recording signal extent, undertake attenuation to signal extent namely, it is ALC circuit to circuit of pilot of recording signal extent.

(3) after ALC circuit enters control state, requirement recording signal heals big, heal to the attenuation of signal big.

Narrate a specification through going up knowable, him requirement in circuit analysis has more comprehensive knowledge side, this need is in continuous study accumulate over a long period.

2. Circuit job principle analyses specification of train of thought

About the analysis of principle of job of this one circuit train of thought basically explains a few following:

(1) if do not have VD1 this one spur track, the recording signal that outputs from class recording amplifier is added in recording amplifier of the 2nd class entirely. But, had VD1 after this one spur track, the recording signal that outputs from class recording amplifier can be passed likely C1 and guide the VD1 that connect sheds the ground to carry, form the billabong attenuation of pair of recording signal.

(2) the 2nd key that circuit analyses is VD1 the particular case of the right billabong attenuation that this one spur track outputs signal to class recording amplifier. Apparent, the capacitance C1 in spur track is the electric capacity with a larger size (polarity of the line out in C1 circuit symbol, showing C1 is to electroanalysis capacitance, and electroanalysis the size of capacitance is larger) , so C1 assumes route to recording signal, the VD1 in showing this one spur track is the key that has billabong attenuation to recording signal yuan parts of an apparatus.

(3) should understand from inside analysis of circuit of billabong spur track a bit: From the signal that class recording amplifier outputs, if be gotten from billabong of VD1 spur track much, so the recording signal that flows into recording amplifier of the 2nd class is small, conversely big.

(4) VD1 existence guides with end two kinds of circumstances, billabong action is not had to recording signal when VD1 ends, be in guide billabong undertakes to recording signal when connecting.

(5) receive on VD1 anode have resistor R1, it controls voltage to VD1, apparent this voltage is controlling VD1 to guide connect or end. So, the voltage that R1 delivers is to analyse VD1 to guide connect, cut-off crucial place.

The difficulty that analyses this circuit is guide in VD1 after connecting, used diode to guide after connecting its to resistor and guide electrify sheds the relation character between to undertake circuit is analysed, namely of diode healing to electric current big, its are healing to resistor small, the electric current that has shed VD1 heals big, the resistor between its anode and negative pole heals small, conversely big.

3. The general analysis method that dominates circuit explains

To control the analysis of circuit should be divided into a variety of circumstances normally, distribute control signal into for example big, medium, small wait for a few kinds of circumstances. With respect to this one circuit character, control voltage Ui should be divided into to the control of diode VD1 following a few kinds of circumstances.

(1) when there is recording signal in circuit, ui of dc control voltage is 0, diode VD1 ends, VD1 does not have an influence to circuit job, the signal that class recording amplifier outputs can be added in recording amplifier of the 2nd class entirely.

(2) when the recording signal in circuit is lesser, ui of dc control voltage is lesser, guide without what be more than diode VD1 electrify is pressed, can’t make diode VD1 guides so, the signal that right now diode VD1 outputs to class recording amplifier also does not have billabong action.

(3) when the recording signal in circuit is bigger, ui of dc control voltage is bigger, make diode VD1 guides, recording signal heals big, ui of dc control voltage heals big, VD1 guides connect degree to heal deep, the internal resistance of VD1 heals small.

(4) VD1 guides after connecting, the internal resistance of VD1 drops, the one part in the recording signal that class recording amplifier outputs is mixed through capacitance C1 guide ground be goinged to by billabong carries the diode VD1 that connect, VD1 guides more deep, its internal resistance heals small, the right cent discharge that outputs signal to class recording amplifier heals big, realize automatic n control.

(5) of diode VD1 guide connect degree to suffer dc to control voltage Ui, and dc controls voltage Ui to believe number size as the recording in circuit change and change, so the internal resistance change of diode VD1 suffers recording signal size to control actually.

4. Breakdown detects method and circuit breakdown analysis

The method that to this one circuit medium diode breakdown detects is to undertake fungible checking, if performance is bad,also can affect the control result of circuit because of diode.

When diode VD1 open a way, nonexistent control action, sound can appear a little while to rise and fall smally a little while greatly when big signal recording at this moment shape is lack fidelity, in recording signal very hour recording can normal.

When diode VD1 puncture, action of nonexistent also control, at this moment recording voice is very small, because register phonic signal,be gone to by the diode VD1 billabong of puncture the ground.

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