12/18/2023 0 Comments Npn vs pnp transistorSee the link I provided above for some pictures. I believe the emitter has to be more doped than the base and the collector. For a pnp junction a common layout is with a large n-type rectangular region, and two small p-type regions separated from each other at the top. In practice, the regions generally are not layed out linearly (at least not in CMOS). A p-type semiconductor has what are referred to as holes by introducing an impurity with less valence electrons than Si, and is an electron acceptor. An n-type semiconductor has excess electrons by introducing an impurity with more valence electrons than Si (Si has 4 valence electrons). Doping is when you introduce impurities into an otherwise pure Si (Silicon) crystal creating an extrinsic semiconductor with an excess of one polarity. P-type and n-type are two types of semiconductor doping. Now for the nitty gritty and the analog side. That should explain the function difference. With a pnp junction it is the opposite, when the base is low the switch is closed and current can flow, and when the base is high the switch is open and current cannot flow. With a npn junction, when the base is low the switch is open and current cannot flow, and when the base is high the switch is closed and the current can flow. One can apply either a high or a low input to the base. Let's try a more digital explanation too. In a pnp transistor the emitter and collector are reversed. Your high Vcc, generally will go into one of the transistors collectors and the emitter of that transistor will feed into another collector, make sense? Probably not with out figures. Your high and low voltage is dependent on what transistor-transistor logic (TTL) family you are using. In digital design the base is your on off switch. If current is applied to the base, than current is allowed to flow between the collector and the emitter. Let's call the current going into the collect Ic, the current going into the base Ib, and the current exiting the emitter Ie (Direction is important for signs). Digital circuits are a lot easier to deal with. Keep reading if you care about analog circuits. A npn has an n-type, a p-type, then an n-type again.įor your question, I am going to assume you are talking about a digital circuit. In more detail, for a pnp bipolar junction transistor (BJT) has a basic structure of p-type (emitter), n-type (base), then p-type (collector). I'll answer your question first and then go into more detail. ![]() Top left circuit shows that bipolar transistors are all about current, therefore you can connect 100V to collector (refer to datasheet first) and transistor will not pass anymore than Ie=Ib+(hFE x Ib), therefore voltage drop across C-E will be in this case 98V, and when you multiply it with 30mA which flows through transistor, youll get not much less than 3W of heat, which will successfuly destroy transistor w/o any heatsink.I'll probably talk about more than you asked by "functional difference." I understand the Digital side, but the Analog information below is what I understand and is a bit incomplete. You can multiply hFE connecting transistor into darlington circuit when current to one npn transistors base is sourced from another transistors emmiter, shown in circuit on right side. When you apply 1mA to base of npn with hFE 100, transistor opens and is capable to handle up to 100mA. Remember, current has to flow in direction of arrows. In case of PNP is it simmilar just apply negative voltage to E-B. In case of NPN, E-B is basically diode so you have to apply positive voltage above ~0.7V and transistors opens. Source current into the base of npn transistor or Ideal transistor is perfect isolant until you
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