Transistor is the parts of an apparatus of the foundation in imitate circuit, to electronic engineer, the condition that knows transistor work and the working status that judge transistor are special foundation, the article will take everybody to learn together or review.
One, the condition that transistor works
1, collector resistor Rc:
In amplifier of common emitter voltage, output end to take out transistor by) of signal of trends of Use(of enlarge signal voltage, need is strung together in collector receive Rc of a resistor. Come so, when Ic of collector electric current is passed, icRc of one voltage drop arises on Re, output voltage is taken out between C-e of canal of You Jing body, namely Usc=Uce=Ec-IcRc, so Use also is mixed IcRc — kind happens along with what input voltage Ui and corresponding ground changes.
2, Ec(of collector power source or Vcc) :
The knot is in the market report that Ec assures transistor to slant reversely buy, make pipe job is magnifying condition, make weak signal turns into strong signal. The origin of energy is those who rely on Ec maintain, is not transistor oneself.
3, Eb of base power source:
Exile to make transistor produces electricity your work is used, besides make sure electric knot is in collect to slant reversely outside buy, still must make emissive knot is in to slant buy, the action of Eb is offerred to emissive knot namely to bias voltage, cooperate proper base class resistor Rb, in order to build an Ib of certain static base electric current. When Vbe very hour, ib=O, exceed some when Vbe only when the value (silicon canal makes an appointment with 0.5V, germanium canal makes an appointment with 0.2V, call doorsill voltage) , pipe begins to guide, occurrence Ib. Subsequently, ib will increase along with Vbe and increase, but, the relation of Vbe and Ib is not linear relation: After Vbe is more than 0.7V, vbe increases little again, ib can increase a lot of. Transistor guides the Vbe that connect is equal to one constant approximately adequately (silicon canal makes an appointment with 0.5V, germanium canal makes an appointment with 0.5V) .
4, Rb of base drift resistor:
In the size of power source Eb already affirmatory condition falls, the block value that changes Rb can change the Ib of static electric current of transistor, also changed Ic of electric current of collector static state and canal to press thereby fall Vce, make amplifier builds appropriate dc job position.
2, the judgement of transistor job status
Crystal dynatron job is magnifying zone time, its launch a knot (between B, E pole) to slanting, market report writtens guarantee (between B, C pole) to slant instead. To the NPN of small-power silicon, appear for Vbe≈0.7V, vbc ” 0V(particular numerical value inspects Ec of power source voltage and the numerical value of concerned component and calm) : To NPN germanium canal, vbe≈0.2V, vbc ” 0V; to PNP model crystal dynatron, the symbol that afore-mentioned voltage are worth is contrary, namely small-power PNP silicon is in charge of Vbe≈-0.7V, vbc ” 0V, to canal of small-power PNP germanium, vbe≈-0.2V, vbc ” 0V. If we are detecting,crystal dynatron discovers in circuit extremely voltage is afore-mentioned numerical value, can judge this dynatron job to be in enlarge area, this part circuit that comprises by this dynatron is enlarge circuit.
Additional, in the oscillating circuit that comprises by transistor, its dynatron also is the job in enlarge area, but the output classics as a result of dynatron chooses frequency resonance return and inphase feedback arrives between its B, C pole, make circuit rises brace up, so the voltage Ube between B, E pole, be less than 0.7V to silicon canal (control) for 0.2V commonly. If we detect,give Vbe ” 0.7V, and the inductance in receiving circuit of the resonance that choose frequency with lead weak point makes circuit stops brace up when Vbe0.7V, can judge this circuit to be oscillating circuit.
2, the job is in end the judgement of the area:
Dynatron job is in end zone time, emissive knot and market report knot all slant to turn over, and in actual circuit, emissive knot also can be 0 slant buy. Such to small-power NPN dynatron, appear for Vbe≤0, vbc ” 0V(particular numerical value basically decides at Ec); of power source voltage to small-power NPN dynatron, appear for Vbe≥OV, vbc≥0V, right now Vce≈Ec, if we detect,the voltage between dynatron of the crystal in giving circuit is afore-mentioned circumstances, can judge this dynatron job to be in end area.
3, the working judgement in saturated area:
Dynatron job is in saturated zone time, its launch knot and market report knot to all be slanting. To canal of small-power NPN silicon, appear to be more than the job to be in slightly for Vbe much 0.7V(the numeric) of enlarge zone time, vbc ” the value that 0V (is not more than Vbe) ; is in charge of to small-power NPN germanium, similarly Vbe≥0.2V(is more than the job to be in slightly the value) of enlarge zone time, vbc ” the value) that OV (is not more than Vbe. To PNP model transistor, the symbol that afore-mentioned voltage are worth is contrary, namely canal of the PNP of small-power silicon, vbe≥-0.7V, vb ” canal of the PNP of value; small-power that 0V(is not less than Vbe germanium, vbe≤-2V, vbc ” the value) that 0V(is not less than Vbe. Usually, right now Vce≈0.3V(silicon is in charge of) or Vce≈0.1V(germanium is in charge of) , the crystal dynatron in if we detect,giving circuit extremely voltage accords with afore-mentioned circumstances, can judge this dynatron job to be in saturated area.
Need points out of a bit is: In some electrons circuit, wait like switch circuit, number circuit, dynatron job is in end change each other between area and saturated area, if attached drawing place is shown. When A dot is 0V, EB is pressed through cent of R1, R2 make base is in negative voltage, emissive knot slants instead; at the same time market report knot also slants instead, so dynatron T ends; is 6V when A dot input when, cent of R1, R2 is pressed make dynatron launchs a knot to slanting, generation is enough big base electric current makes dynatron saturation guides, output carries L to be 0.3V about, right now electric knot also is collect to slanting. We detect when whether circuit is normal, can make A carries the voltage of 0V losing a person and 6V respectively, the dynatron that measures two kinds of circumstances to fall respectively extremely voltage, look to whether accord with afore-mentioned cut-off the circumstance with saturation, it is normal to can judge this circuit to work thereby.
3, brief summary
Crystal dynatron has 3 works area, magnify namely area, end area, saturated area. When circuit is designed, but the requirement according to circuit, let transistor work to magnify in order to comprise in different area circuit of circuit, oscillating circuit, switch, if dynatron changed former regular job position because of some kind of reason, can make circuit works occurrence breakdown of product of wrong; electron, be about to undertake an analysis to breakdown at this moment, the method is narrated to check the working status of dynatron before first job is pressed namely.
Work to transistor detects specificly, should notice at 2 o’clock problem: It is to had better make with internal resistance bigger digital avometer undertakes metrical, measure an error in order to decrease, the change; that dynatron job state has because of the internal resistance introductory note of avometer when avoiding to be measured directly at the same time 2 it is best measure crystal dynatron respectively each are extremely right the voltage of the ground, calculate next the value that gives Ube.Ubc or Uce, avoid to cause the possibility of circuit breakdown.