In a p-n-p junction transistor, what is the source of the base current?
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In a p-n-p diode, the base is n-type and the emitter is p-type. If you forward bias the transistor, it means that V_base < V_emitter (e.g. V_base = 4.3V and V_emitter = 5V). Since the emitter to base is just a p-n diode, you expect such biasing will give you a forward current as in a p-n diode. That means current flows from the emitter to the base.\n\nHowever, if you really want to understand the source of the current, you have to use the concept of electron and hole. (Let me know if you don't know what is hole http://www.kodkodkod.com/index_files/submitquestion.htm). In a p-n junction, holes are injected from p to n and electrons are injected from n to p. They together contribute the the current. Similarly, in a p-n-p transistor, the holes from the emitter are injected from p-emitter to the n-base and electrons are injected from the n-base to the p-emitter. However, most of the holes from the emitter cannot be "collected" by the base and indeed they are "collected" by the Collector. That's why you find that I_E and I_C >> I_B. Therefore, the base current is basically due to the electrons from the base.\n\nOf course, in a non-ideal transistor, some holes from the emitter are collected by the base and there is also reverse current between the base and the collector. As a result, the base current is a summation of all the aforementioned components.\n\nI think my answer might not really tailor-made to your need. It's better to let us know how much you know about the transistors (or your education in EE). The answer to the same question you ask can be very different from high school to research level. Let us know if you need more help!\n\nKodKodKod Learning Consulting - http://www.kodkodkod.com
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For the circuit to work as an amplifier you need to make the collector voltage, move up and down in response to any input signal variations. These changes in collector voltages are coupled out through the capacitor to provide the output voltage signals, This means that in the absence of any input signal the transistor should have a moderate set of applied bias voltages/currents to give room to move up and down under the influence of any input.
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What's to know?\n\nIt's the typical offset voltage, or DC component of the output.  The signal is AC.
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Of course. \nThe actual junction of an N type and P type is what prevents conduction when reverse biased.
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A typical output has a transistor that pulls the output to ground when the output is 0 and a pull up resistor or transistor that drives the output high when the output is 1.\n\nHowever, there are two cases where this might not be desirable. Suppose we have an inverter that we want to use to turn on a 12V light. Sure, you could use a transistor or other switch to do that, but why not use an open collector inverter. This inverter only has the "low side" transistor. So the output is either 0 or floating. If the chip can handle 12V on the input, you can use it to directly turn the light on (it will be on with the output low). The 12V supply would go to the bulb and the other side of the bulb would go to the open collector output.\n\nThe other reason to do this is when you want to drive a lot of outputs into one input. For example, suppose I'm building a CPU. I have an input that causes a register to write its content to the bus. Further, suppose there are 10 reasons you might want to do this. The obvious way is to have a 10 input "OR" gate so that when any of these 10 things occur, the register gets the signal. But an easier way is to make the input active low. Tie a pull up resistor to the input and then drive it with 10 open collector gates. When no one wants to make the register write, the outputs all float and the resistor holds the input high (no action). If any output goes low (or multiple outputs, for that matter), the input goes low and the action occurs. This is often known as wired-OR.\n\nYou might find The Art of Electronics useful. You can read my review of this fine book at http://www.wd5gnr.com/books.htm (I didn't write it, BTW).
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The movement of a hole in p-type semiconductor is in fact the movement of electrons sequentially filling a valence band vacancy.\nThis means that holes tend to move at a lower speed than electrons would in the same material with the same electric field applied.\nWe measure the effective mass of the hole by applying a field to the material and seeing how fast the holes accelerate (Newton's Law)\n\nIf you look at the characteristics of complementry transistors, which are being sold as matched pairs, you will see the extra mass of the hole manifests as an inferior characteristic in the ptype carrier transistor or FET.\n\nA p-type carrier is a hole in a semiconductor.\nA positron is a hole in space that can be filled by an electron.  The hole in space has a mass, velocity and the opposite quantum numbers of the electron.\nHoles and positrons are not the same animal!!!!!!
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Semi-conductor diodes have a non-linear and asymmetric current flow response to applied voltage. Basically they allow much greater current to flow in one direction over the other. It is based on some pretty heavy physics, but can be modeled by considering the junction between N type doped semiconductor and P type doped semiconductor where the majority carriers on one side are positive, and the majority carriers on the other are negative. When you bias the junction in a certain way the carriers on each side of the junction cancel each other out and you get very limited current flow. When you bias the diode the other way the carriers don’t cancel and you get much higher current flow for the same applied voltage.\n\nI assume you don't want to know about vacuum tube diodes of old. They are based on a very different physical property.\n\nHope this helps.
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The voltage, current and resistance are related by the equation, “Change in voltage = Change in current x Change in resistance.” \nIf we have a device which changes the resistance without allowing a change in current then change in voltage is directly proportional to the change in resistance. Transistor is such a device. \nIn an amplifier one gets an amplified output signal for a small input signal. Transistor is used in amplifier. It transforms the output resistance so as to keep the output current nearly equal to the input current. That is why it is called transistor. (Transforms resistor)\nWhen a weak pulse is applied across the input of an amplifier having a transistor, there is a small change in the input current, voltage and resistance. But the transistor increases the resistance in the output, but keeps the output current same as the input current.\nCurrent being the same, we get an amplified voltage.
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x\n\nthe answer below is just for voltage - see my graph above - it is quite accurate. here it is again, larger: X
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TTL (Transistor-Transistor Logic) is a name for type of logic circuits which are constructed using the bipolar transistors. \n\nIn general the bipolar transistors such as the NPN and PNP transistors are current operated devices. In these types of transistors, when used for digital logic circuits, typically the input voltage is applied across the Base-Emitter junction. As a result of this a small base current is produced in that junction. This small base current is magnified by the transistor's current gain factor B(called Beta), resulting in a large amount of collector-emitter current. This is basiclly how a TTL switch works.\n\nThe TTL family of circuits are generally very fast, but this speed comes at the cost of higher power dissipation. Also, a typical TTL logic gate circuit requires multiple transistors and other passive components such as resistors. This results in lower number of gates that can be put on an IC built using TTL family.\n\nThe CMOS(Complimentary Metal Oxide Semiconductor) family of logic circuits are buit using Metal Oxide Semiconductor(MOS) Field Effect Transistors (FET). These types of transistors are voltage operated devices. A typical CMOS logic gate circuit can be constructed using as little as two MOSFET transistors (A CMOS Inverter) resulting in a much higher density of logic gates that can be put on an IC.\n\nAlso, CMOS gates use much much lower power to operate compared to the TTL gates because no resistors are required to build such circuits.\n\nCMOS logic also allows much higher operating voltages compared to the TTL family.\n\nOne drawback of CMOS family is that they are slower than the TTL family, however these days this may no longer be true.
532709
the minimum current needed to cause the thyristor to latch/switch state
767508
http://en.wikipedia.org/wiki/Zener_diode
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Wow, I can't believe you have been waiting so long for an answer.\n\nThere are a couple of papers you can review:\n\ne.g. http://www.nsti.org/publ/MSM2002/348.pdf#search='frequency%20mosfet%20parameter'\n\nand here also:\nhttp://www.freewebs.com/anishamukherjee/Papers.htm\n\nThere is a tool here, but you need to pay, and I have not used it myself:\n\nhttp://www.highbeam.com/library/doc0.asp?docid=1G1:79591050&refid=ink_tptd_mag_test1&skeyword=&teaser=
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It's going to be one or the other, it doesn't change during function.\n\nThe junctions are determined when the transistor is manufactured, it's part of the physical structure of the device, so it's polarity does not change.
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This is a very simple circuit.\nhttp://www.rason.org/Projects/fmkeyer/fmkeyer.htm
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PNP: Semiconductor crystal structure consisting of an N-type region sandwiched between two P-type regions, as commonly used in bipolar transistors\nwhereas\nNPN transistor: A transistor which has a base of P-type silicon sandwiched between an emitter and a collector of N-type silicon.
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Read this page. I hope it will help you.\nhttp://www.powerdesigners.com/InfoWeb/design_center/articles/MOSFETs/mosfets.shtm