The output curve of field effect transistor (example is unscrambled)
[introduction] how does the output curve of field effect transistor understand? Field effect canal outputs characteristic curve cent to be 3 areas: Alterable resistance area, constant current area and puncture area. When VDS is lesser, job of field effect canal is in alterable resistance area, ID makes linear change along with VGS approximately. When VDS is bigger, the job is in constant current area, ID keeps stable, do not follow the change of VGS and change. Be more than some when VDS when critical value, enter puncture area, ID begins to increase quickly, field effect canal cannot work normally. What everybody is helped deepen the output curve of pair of field effect transistor below through interlocution of a few example is cognitive.
The output curve example of field effect transistor one:
Ask: If pursue, vgs=8V, vds=20V when, id is close to 300A. How does the test come out this data? Want to know me to receive the voltage weak point of 12V in D, between S, the instant with respect to cartridge igniter.
Answer: The partial curve that you see is to show tubal core is enclosed absoluteness, temperature tubal core is constant the curve of ideal electric current when be 25°c, of IR have a test commonly, domestic Mos did not do a test commonly, basically be academic curve. But TO220 is other perhaps enclosed Mos is enclosed limitation, cent of actual Id size is planted, it is the limitation that is enclosed, 2 it is the limitation that is in charge of core temperature, the application of net of official of OK and referenced IR before you do this test takes notes, the test condition that perhaps goes up according to Pdf is done. Say by you, won’t do commonly, if 12v test source current is enough big, guide completely when Mos when connecting, its Id will be very tall, bring about Mos power comsumption to cross big damage thereby, because this test that you do does not have what meaning.
G of canal of additional outfield effect is extremely cannot impending, otherwise extremely easy as a result of inductive voltage, make pipe guides, guide the internal resistance when connecting is very low, if test voltage internal resistance is very little also, surely cartridge igniter is undoubted.
The output curve example of field effect transistor 2:
How does modular report output characteristic curve and move character curve to divide field effect canal according to theirs?
Through outputting characteristic curve and move character the curve distinguishs before field effect is in charge of, need to understand a concept above all, field effect canal is to press accuse model parts of an apparatus, it is distinguished at ambipolar model transistor (stream accuse model parts of an apparatus) , it is OK that the grid when field effect provides the job needs a voltage only commonly, electric current is very small perhaps be 0. So, want to come true this a little bit, canal of knot field effect and MOS used different method to achieve this result, brought about its character curve to differ.
Knot field effect is in charge of, use a between grid and raceway groove retrorse diode, bring to bear on on diode retrorse voltage, when using diode to work reversely, the characteristic with very small electric current, implementation pressing dominates the result, when so knot field effect provides the job, grid controls voltage UG to always need to make sure that diode works reversely, namely N raceway groove, grid voltage is negative, voltage of grid of P raceway groove is. As to leakage extremely voltaic polarity, can pass N raceway groove, n delegate is lost, exterior electric current flows into D pole, voltaic direction is namely, electric current of P raceway groove pours out of D pole, voltaic direction is namely negative. So, the curve that pursues below is very good memory.
And MOS canal, snap block of the insulation between grid and raceway groove directly, do not have any electric current to pass. Press control N raceway groove by normal positive electricity so, negative voltage controls the principle of P raceway groove. When the job, voltage of grid of N raceway groove is, voltage of grid of P raceway groove is negative. The judgement method of voltaic direction and knot canal is same, n raceway groove, n delegate is lost, exterior electric current flows into D pole, voltaic direction is namely, electric current of P raceway groove pours out of D pole, voltaic direction is namely negative. Can decide the characteristic curve that MOS is in charge of. As to increase model and extinct model how to distinguish, should see control curve and Y axis have across only can, namely, when UG=0, leakage pole electric current is 0, it is namely extinct model, when UG=0, leakage pole electric current is 0, it is namely increase model. Following plan institute are shown.
The output curve example of field effect transistor 3:
Transfer characteristic curve according to what field effect is in charge of, the raceway groove of what type is how judging it?
Judge N above all model or P, this is simple, should observe the curve is only in coordinate upper part or lower part, upper part is N raceway groove (set) ; Come to increase then model extinct still model, simple also, increase model it is only inside 1/4 interval coordinate, and extinct model be in half coordinate commonly inside; Additional, about the knot model still be isolated from bar it is to treat curvilinear range, receiving those who be bordering on reference axis indefinitely is a knot model, insulation bar curve is have initiative place go up in reference axis, and curvilinear extent is steeper.
Basis of field effect canal is electric of raceway groove have be in charge of for knot field effect without cent (JFET) be in charge of with effect of insulation bar field (MOS) two kinds of main types.