bipolar junction transistor (BJT)

A bipolar junction transistor (BJT) is a type of transistor. It is a three-terminal device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons and holes.

Although a small part of the transistor current is due to the flow of majority carriers, most of the transistor current is due to the flow of minority carriers and so BJTs are classified as 'minority-carrier' devices.

An NPN transistor can be considered as two diodes with a shared anode region. In typical operation

• the emitter–base junction is forward biased
• the base–collector junction is reverse biased

In an NPN transistor, for example, when a positive voltage is applied to the base–emitter junction

• the equilibrium between thermally generated carriers and the repelling electric field of the depletion region becomes unbalanced
• allowing thermally excited electrons to inject into the base region
• These electrons wander (or "diffuse") through the base from the region of high concentration near the emitter towards the region of low concentration near the collector
• The electrons in the base are called minority carriers because the base is doped p-type which would make holes the majority carrier in the base.

The base region of the transistor must be made thin, so that carriers can diffuse across it in much less time than the semiconductor's minority carrier lifetime, to minimize the percentage of carriers that recombine before reaching the collector–base junction. To ensure this

• the thickness of the base is much less than the diffusion length of the electrons

The collector–base junction is reverse-biased, so little electron injection occurs from the collector to the base, but electrons that diffuse through the base towards the collector are swept into the collector by the electric field in the depletion region of the collector–base junction.

A BJT consists of three differently doped semiconductor regions

• the emitter region
• the base region
• the collector region

These regions are, respectively, pn type and p type in a PNP, and n type, p type and n type in a NPN transistor. Each semiconductor region is connected to a terminal, appropriately labeled:

• emitter (E)
• base (B)
• collector (C)

The diagram shows the schematic representation of an npn transistor connected to two voltage sources. To make the transistor conduct appreciable current (on the order of 1 mA) from C to E, V_BE must be above a minimum value sometimes referred to as the cut-in voltage. The cut-in voltage is usually about 600 mV for silicon BJTs, but can be different depending on the current level selected for the application and the type of transistor.

In the diagram, the arrows representing current point in the direction of the electric or conventional current—the flow of electrons is in the opposite direction of the arrows since electrons carry negative electric charge. The ratio of the collector current to the base current is called the DC current gain. This gain is usually quite large and is often 100 or more.

As the applied collector–base voltage (V_BC) varies, the collector–base depletion region varies in size. An increase in the collector–base voltage, for example, causes a greater reverse bias across the collector–base junction, increasing the collector–base depletion region width, and decreasing the width of the base. This variation in base width often is called the "Early effect" after its discoverer James M. Early.

Narrowing of the base width has two consequences:

• There is a lesser chance for recombination within the "smaller" base region.
• The charge gradient is increased across the base, and consequently, the current of minority carriers injected across the emitter junction increases.

Both factors increase the collector or "output" current of the transistor in response to an increase in the collector–base voltage.

In the forward active region the Early effect modifies the collector current (i_C) and the forward common emitter current gain (β_F) as given by the following equations:^{[citation needed]}

Where

• V_CB is the collector–base voltage
• V_A is the Early voltage (15 V to 150 V)
• β_F0 is forward common-emitter current gain when V_CB = 0 V

pn junction diode

do you know how actually pn junction diode work?

here i have the theory how it does..hehe..actually soalan ni ditanya masa aku g interview kt NS aritu..huhu..

In a p-n junction, without an external applied voltage, an equilibrium condition is reached in which a potential difference is formed across the junction. This potential difference is called built-in potential V_bi.
In an equilibrium PN junction (Figure 1.0), electrons near the PN interface tend to diffuse into the p region. As electrons diffuse

• they leave positively charged ions (donors) on the n region
• Similarly holes near the PN interface begin to diffuse in the n-type region leaving fixed ions (acceptors) with negative charge
• The regions nearby the PN interfaces lose their neutrality and become charged, forming the space charge region or depletion layer

Figure 1.0: A p-n junction in thermal equilibrium with zero bias voltage applied.

The electric field created by the space charge region opposes the diffusion process for both electrons and holes. There are two concurrent phenomena:

• the diffusion process that tends to generate more space charge
• and the electric field generated by the space charge that tends to counteract the diffusion.

The carrier concentration profile at equilibrium is shown in Figure 1.1 with blue and red lines. Also shown are the two counterbalancing phenomena that establish equilibrium.

A PN junction in thermal equilibrium with zero bias voltage applied. Under the junction, plots for the charge density, the electric field and the voltage are reported.

pn junction diode have 2 bias which are foward bias and reverse bias

• Forward-bias occurs when the P-type semiconductor material is connected to the positive terminal of a battery and the N-type semiconductor material is connected to the negative terminal. This reduces the width of the depletion zone.

• Connecting the P-type region to the negative terminal of the battery and the N-type region to the positive terminal, produces the reverse-bias effect. Therefore the depletion region widens

keje keje dimana ko keje

adoyai...ape le nk jd ngn aku ni...lh dpt keje ke x ni...huhu...arini aku ade interbiu kt NS tuk jwtn CAD engineer..pg ni aku bgn awal tau semata2 nk g interbiu 2..dh siap semua aku kuar le nk pkai kasut..ngok2 langit dh gelap nk ujan le 2..br kul 7.30pg je wktu 2..kilang NS 2 br 5 minit jln dh smpai dh..mak aku kte g le sblm ujan ni..mau xmau kne le awal..lps 5 minit je aku gerak dh smpai kt NS 2..br kul 7.40..awal lg 2..kne le aku nunggu kt guardhouse dia..slmt le ade waiting room kt gaurdhouse2..dh smpai kul 8 masih aku sorg je kt c2..trpikir gk aku mne yg lain..rupanye sehari sorg je dorg interbiu

Smpai kt HR office ttiba ade dorg tnye bkn aku kne dtg ptg ni kul 3 ke..pulak!!dh glabah dh aku..aku lupa lk dia ade ckp ke x interbiu 2 kul bpe..slalu aku g interbiu awal2 pg..heheh..silap le 2..tp dorg kte xpe le..dorg srh isi borg ngn amik test..aku pkir senang je r..dh abis aku isi borg aku bkk le ktas test 2..1st soalan dia tnye curve characteristic zener diod..ternganga aku skjp..ni aku blaja mse form 5 dl ni..mne aku nk ngat dh..aku sbar lg..aku selak dan selak dan selak..aku geleng kepala dan terpikir..klo le ketas jd ketas final exam elektronik analog aku dl kompom semua failed..gila susah test ni sioooot!!!!!..aku dpt jwb bpe kerat je..pergghh..aku dh mula pkir dh leh ke x aku dpt job ni...huhu..korg tau x buat gate not dr gabungan N-MOS transistor?..huuu..aku xdpt jwb..mmg yg xnh ade dlm otak aku pn ade kt ketas 2..huuhu..abis le aku cmni..

dh abis sume ade cik sorg ni bwk aku g jmpe ngn manager bhgn CAD ni..dan sesi interbiu bermula..dan hasil nye sme le sperti interbiu2 yg lepas..huhuhu..cmne le aku nk dpt keje cmni..huhuhu...

hai...ape le nk jd ngn aku ni...ble le aku lh dpt keje ni..
ke nk smbung lg ek..pikir2 jgn xpikir..

my lovely little gurl

hehe..ni anak buah aku yg pertama..

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tp ktorang pgl di wish sje..xpun iman

seorang yg comey tp mmg xreti duk diam..

dalam otak dia msti ade benda yg nak dibuat..

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gambar ni waktu wish br bebelas ari...

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klo nk ltk sme koleksi gmbar dia xmuat blog ni..hehe..

xtau le aku...heheh..

hehe..dh lme aku xngarut dlm blog ni kn..aku ngok2 blk dh nk 3 bulan kn..hehe..xde mood r nk tulis blog ni..keje masih xde..dh 5 bulan menganggur ni..tp rezeki kembali kepada ku..aku dapat interbiu!!!..hehe..kt mlake lk 2..bgs le..bkn cm aritu..duit abs tp keje tarak..huhu..aku dpt interbiu kt kilag NS (National Semiconductor)..dia bg post CAD engineer..ni mmg rezeki ni..kne sambar ni, aku mg minat ngan CAD ni(aku ye FYP dl pn CAD gk)..2 yg aku suka..bkn 2 aje tau..aku dpt twran pereksa kemasukan pgwai awam sbtu nnt..2 ari lepas interbiu 2..kt mlake gk(MITC)..mmg xkuar duit r aku cmni, dh le sengkek thp babeng dh ni..tuk 2 2 keje ni aku wt ulangkaji 2..ngalahkn aku wt study mse blajar dlu..harap2 le dpt..hehe..

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ni slideshow aku wktu 1st sem

muka cm bbdak je lg ni haa..excited dpt masuk U..hehe..tp mse aku msuk UMT 2 KUSTEM lg..aku dh 2 taun blajar br dpt title U..tp sempat gk aku grad bertitle UMT..hehe..

ni slideshow aku wktu 2nd sem

wktu ni aku dh rmai kwan dh..dl waktu 1st aku duk ngn bbdk kos lain..aku terdaftar awal, so dpt le aku roomate kos maritim..bbdak kos aku lk ngt aku ni ganas, so xramai le yg kwan ngan aku..1st fren bdk kos aku si apis..tp sem 3 dia 2kar kos m3 kom..so jd le bdk taun 1 blk mamat 2..bdk pompuan yg aku mula2 knl si azue ngan ilmi..seminggu lps 2 amy msuk ngn ttba n trus le rapt ngan aku..hehe..drpd aku trun mkan ngan mamat maritim mse mula2..dh knl dorg ni aku pn trn le makan ngn minah2 ni..smpai bbdak maritim pn kutuk aku..tp xpe kutukan mmbina..hehe..

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ngok..mmne aku g pn muka2 yg sme gk ikut..hehe..dh nme pn kawan kn..

itu le sjarah idup aku waktu aku mmula masuk kt UMT..opss, KUSTEM lg wktu 2..hehe..pape pn fren 4ever k..dh abis blajar pn ttp keep in touch lg ktorang..hehe..caiyok2!!

p/s: sambil bc blog ni dngar le lagu arti sahabat dr nidji yee..baru best..aku nk upload ade yg
akustik nye je..xbest ngat..hehhe..