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Explain why the collector voltage is approximately zero when a transistor has a collector-emitter short?
The collector voltage is not necessarily approximately zero when a transistor has a collector-emitter short. It depends on whether or not there is an emitter resistor.
A typical collector-emitter circuit has two resistors, one in the collector and one in the emitter. One or both of them might be zero, i.e. not present, depending on design requirements. The collector-emitter junction represents a third resistor, the value of which is dependent on base-emitter vs collector-emitter current ratios and hFe.
If the collector-emitter junction is shorted, then this circuit degrades to a simple voltage divider, or single resistor, and the collector-emitter voltage differential will be approximately zero. Simply calculate the voltage based on the one or two resistances.
Results could be different than calculated, if the resistors are small in camparision to the shorted impedance, and it could be different depending on the base to emitter or collector relationship in that fault state, though the latter case is usually negligible due to the relatively high resistances of the base bias circuit.
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Explain the operation npn transistor when used as amplifier.. and explain the basic operation of NPN when used as switch?
The NPN transistor when used as an amplifier is operating in linear mode, and, when operating as a switch, in saturated mode.In the following discussion, base currrent means base-emitter current, while the base is more positive than the emitter, and collector current means collector-emitter current, while the collector is more positive than the emitter. There is base-collector current, but we are going to ignore it for now - besides, we are going to discuss class A, common emitter, configuration.The PNP transistor is very similar. Everything is backwards, including Vcc, which is now -Vcc, or appropriate reconfiguration. The rules are the same - just backward.In switched or saturated mode, the ratio of base to collector current is far greater than beta-dc, or hFe, so the transistor is operating way out of its linear mode. We call that saturated mode, and the transistor is essentially either fully on or fully off, and therefore operating as an on-off switch.The rest of this discussion will focus on linear or amplilfier mode.If the ratio of base to collector current is less than beta-dc, or hFe and, if both base and collector voltage are greater than cutoff voltage, then the transistor is operating in linear mode. Well, sort of, for best linear mode, we look at the data sheet, or make empirical observations, and we pick the base and collector currents that are centered between the base knee and the collector knee, i.e. "in the middle of" the linear region.In this mode, a very small base current can control a much larger collector current, and, most importantly, a very small change in base current can create a much larger change in collector current.In the theoretical case, for example, where the emitter is grounded and where hFe is 100, then 1 mA of base current translates to 100 mA of collector current, and 2 mA of base current translates to 200 mA of collector current. Problem is, that hFe varies amongst even so called identical transistors, and hFe varies as a function of temperature as well.So, in the practical case, an emitter resistor is added to stabilize the transistor and place limits on the need for hFe of a particular value. Done properly, this will yield predictable gain for various transistors and for various temperatures.Now, lets look at how gain works in the practical sense. The base voltage is also a known delta above emitter voltage. Yes, temperature will affect this, but proper design can make this a negligable factor. The emitter current times the emitter voltage results in a known voltage. By Norton's current law, the base current and the collector current add up to be the emitter current, but by hFe, the base current is very much smaller than collector current, meaning that the really important part is that collector and emitter current are the same for all practical purposes.So, now add a collector resistor. Ignoring base current, the collector/emitter circuit is a series circuit, and Norton's current law, reinterpreted for series circuits, says the two resistors have the same current. Think about what that means; if the current in both resistors is the same, then the ratio of the voltage across the two resistors is proportional to their value. The gain of the amplifier is collector resistor divided by emitter resistor. That is critical knowledge. Again, base current enters into the equation but, if hFe is high enough, it does not matter.All that is left, then, is to bias the base. You want to pick a base voltage (current) that places the collector current in the center (or in an appropriate point) of the linear region. Choose a nominal hFe, divide by collector current, and you get an approximation of what base current bias should be. Choose a resistor divider to match, keeping in mind that the two resistors (base to Vcc and base to Gnd) in parallel will reflect your effective input impedance.Review everything, particularly your power levels. To calculate the power through the collector/emitter junction subtract collector resistor voltage from emitter resistor voltage from Vcc, and you get collector/emitter voltage. Multiply that by collector current, and you get power dissipated by the transistor in nomial bias condition.Play with the values until you have what you want. You could even set this up in a spreadsheet.Last, but not least, there is a base bias voltage. If you are going to amplify something, you need to maintain that nominal bias voltage. Connect a series capacitor between the base and the input point and you will be able to operate from an AC signal that is zero referenced. Just pick the RC time constant appropropriate for your application.Similarly, there is a collector bias, so, if you want an AC output zero referenced, use a series capacitor also in between the collector and the ouput.This is an AC coupled, inverting amplifier. There are DC coupled non-inverting versions, but they are more complicated, requiring more than one transistor, and this answer does not address them. Good luck!
What are the operating regions of transistors and explain it?
There are three operating regions in transistor...(Transfer-Resistor)1)cutoff region2)Active region3)Saturation regionActive region:It is the central region where there are curves and where slope is taken.it is the region where emitter-base is forward biased and collector-base is reversed bias.Cutoff region:It is the region which lies below the curves. it is the region where the transistor is in OFF state.in this region both emitter-base and collector-base is reversed bias(i.e no sufficient voltage is applied so that the voltage does not break the DEPLETION region).Saturation region:It is the region situated to near the active region near Y-axis.It is the region in which the both emitter-base and collector-base is forward biased.Based on application the transistor is decided where to lie.for example transistors are made to lie in active region to make it as amplifier.when transistors are used as switch it is made to lie in saturation region(when switch is made as ON) and cut-off region(when switch is made as OFF).....Thanks guys for reading this. please forgive me if there are any mistakes....ANSWER: In actuality there is only one REGION The other regions are not operating regions but rather states. An operating region on a transistor is set up during design of an amplifier to transfer maximum undirstorted power to the load. This design is called BIAS
Circuit description of inverter?
Inverters can be made in many different ways. You can use CMOS transistors. Having a p-fet transistor pulled high and a n-fet transistor pulling low. Both gates are connected together as inputs. Output is the node between the n-fet and p-fet. The other way is using CML (Current Mode Logic) which uses Bi-polar transistors. Its design rather steers current. Hard to explain the physical layout but you should be able to google "inverter cml". CML is much more robust, drives better, and it is faster.
Explain the construction and working of a CRO?
explain cro construction and working
How do you explain the principle of working of ULN2803?
Explain the workin principle of uln and its abbreviation
Explain the saturation region in common emitter transistor?
A: As base current increases the collector current increases to a point where any more base current will not increases the collector current at hat point the transistor is saturated whereby current may flow in both direction and the two diodes will essentially be in a parallel mode and the voltage drop from emitter to collector will reflect the status as a low voltage drop.
Explain MOSFET elaborately?
MOSFET = metal-oxide semiconductor field effect transistor That in itself is quite elaborate.
Explain briefly about field effect transistor?
Think of a solid state triode vacuum tube, the mathematical model is almost identical.
Why you are using three transitor in linear voltage rgulator?
You do not have to; a simple power supply can use as few as 1 transistor. Supply a drawing, or explain your schematic.
Explain the operation npn transistor when used as amplifier.. and explain the basic operation of NPN when used as switch?
The NPN transistor when used as an amplifier is operating in linear mode, and, when operating as a switch, in saturated mode.In the following discussion, base currrent means base-emitter current, while the base is more positive than the emitter, and collector current means collector-emitter current, while the collector is more positive than the emitter. There is base-collector current, but we are going to ignore it for now - besides, we are going to discuss class A, common emitter, configuration.The PNP transistor is very similar. Everything is backwards, including Vcc, which is now -Vcc, or appropriate reconfiguration. The rules are the same - just backward.In switched or saturated mode, the ratio of base to collector current is far greater than beta-dc, or hFe, so the transistor is operating way out of its linear mode. We call that saturated mode, and the transistor is essentially either fully on or fully off, and therefore operating as an on-off switch.The rest of this discussion will focus on linear or amplilfier mode.If the ratio of base to collector current is less than beta-dc, or hFe and, if both base and collector voltage are greater than cutoff voltage, then the transistor is operating in linear mode. Well, sort of, for best linear mode, we look at the data sheet, or make empirical observations, and we pick the base and collector currents that are centered between the base knee and the collector knee, i.e. "in the middle of" the linear region.In this mode, a very small base current can control a much larger collector current, and, most importantly, a very small change in base current can create a much larger change in collector current.In the theoretical case, for example, where the emitter is grounded and where hFe is 100, then 1 mA of base current translates to 100 mA of collector current, and 2 mA of base current translates to 200 mA of collector current. Problem is, that hFe varies amongst even so called identical transistors, and hFe varies as a function of temperature as well.So, in the practical case, an emitter resistor is added to stabilize the transistor and place limits on the need for hFe of a particular value. Done properly, this will yield predictable gain for various transistors and for various temperatures.Now, lets look at how gain works in the practical sense. The base voltage is also a known delta above emitter voltage. Yes, temperature will affect this, but proper design can make this a negligable factor. The emitter current times the emitter voltage results in a known voltage. By Norton's current law, the base current and the collector current add up to be the emitter current, but by hFe, the base current is very much smaller than collector current, meaning that the really important part is that collector and emitter current are the same for all practical purposes.So, now add a collector resistor. Ignoring base current, the collector/emitter circuit is a series circuit, and Norton's current law, reinterpreted for series circuits, says the two resistors have the same current. Think about what that means; if the current in both resistors is the same, then the ratio of the voltage across the two resistors is proportional to their value. The gain of the amplifier is collector resistor divided by emitter resistor. That is critical knowledge. Again, base current enters into the equation but, if hFe is high enough, it does not matter.All that is left, then, is to bias the base. You want to pick a base voltage (current) that places the collector current in the center (or in an appropriate point) of the linear region. Choose a nominal hFe, divide by collector current, and you get an approximation of what base current bias should be. Choose a resistor divider to match, keeping in mind that the two resistors (base to Vcc and base to Gnd) in parallel will reflect your effective input impedance.Review everything, particularly your power levels. To calculate the power through the collector/emitter junction subtract collector resistor voltage from emitter resistor voltage from Vcc, and you get collector/emitter voltage. Multiply that by collector current, and you get power dissipated by the transistor in nomial bias condition.Play with the values until you have what you want. You could even set this up in a spreadsheet.Last, but not least, there is a base bias voltage. If you are going to amplify something, you need to maintain that nominal bias voltage. Connect a series capacitor between the base and the input point and you will be able to operate from an AC signal that is zero referenced. Just pick the RC time constant appropropriate for your application.Similarly, there is a collector bias, so, if you want an AC output zero referenced, use a series capacitor also in between the collector and the ouput.This is an AC coupled, inverting amplifier. There are DC coupled non-inverting versions, but they are more complicated, requiring more than one transistor, and this answer does not address them. Good luck!
Explain the needs that led to the development of the artificial satellite and the transistor during the Cold War?
The needs that led to the development of the artificial satellite and the transistor during the Cold War included the high unemployment of the Americans estimated then to be about 14 million, and the need to prove to the world that Americans were innovative.
Explain how a transistor is constructed?
You should really read a book for this technical topic. Also try some free online tutorial, such as http://www.williamson-labs.com/.
What is meant by biasing and explain all the baises?
It means that a voltage is established between two of the three terminals of a transistor, to achieve the desired operation. Since with three terminals you can choose three different combinations of two terminals, there are three different types of biasing.The details vary, depending on the type of transistor used. Also, the details are quite involved. The Wikipedia has some introductory articles; for example the article on "Biasing", or on "Bipolar transistor biasing" if you want to know about biasing for this specific type of transistor.
What are the operating regions of transistors and explain it?
There are three operating regions in transistor...(Transfer-Resistor)1)cutoff region2)Active region3)Saturation regionActive region:It is the central region where there are curves and where slope is taken.it is the region where emitter-base is forward biased and collector-base is reversed bias.Cutoff region:It is the region which lies below the curves. it is the region where the transistor is in OFF state.in this region both emitter-base and collector-base is reversed bias(i.e no sufficient voltage is applied so that the voltage does not break the DEPLETION region).Saturation region:It is the region situated to near the active region near Y-axis.It is the region in which the both emitter-base and collector-base is forward biased.Based on application the transistor is decided where to lie.for example transistors are made to lie in active region to make it as amplifier.when transistors are used as switch it is made to lie in saturation region(when switch is made as ON) and cut-off region(when switch is made as OFF).....Thanks guys for reading this. please forgive me if there are any mistakes....ANSWER: In actuality there is only one REGION The other regions are not operating regions but rather states. An operating region on a transistor is set up during design of an amplifier to transfer maximum undirstorted power to the load. This design is called BIAS
Explain working of ttl for NAND gate?
In the NAND gate, the transistors play the role of the switches. The emitter and the collector voltages vary in the opposite phase.
What is the square root of 42 and how do you explain it?
The square root of 42 is approximately 6.4807. This is because 6.4807*6.4807 = 42 (approx).
Can you explain the main function of the three parts of transistor?
individually, each part has no main function. it's when you use them in conjunction with one another that you get the amplification process. now for an example lets use a simple BJT, say 2N3904 is a NPN transistor. now to better understand picture a diode between the base and the emitter where the anode is at the base and cathode at the emitter. bias the collector at +5V and put the emitter at zero for reference (ground). now lets say you apply 3V to the base, it's going to kick on that "diode" between the base and the emitter and your going to get current to start coming from ground into the emitter. when that current hits the base its just going to keep going (such a small amount is lost through the base that we can ignore it, i'm talkin micro-amp range) the current just goes up through the collector and to your load. now this is an extremely basic example, you'll have to do much more in depth studies to fully under stand how it works.
