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Outrageous
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For a npn transistor, Vb= +0.7V ,Vc=+1.0V , Ve=0
Then my teacher says it is not operating, why is that so?
Thank you.
Then my teacher says it is not operating, why is that so?
Thank you.
Studiot said:I see no reason to believe the transistor as specified is not operating.
Let us suppose a 5 volt supply and a 3k9 collector resistor, then with the figures stated the current through the collector resistor Rc is (5-1)/3.9 milliamps which is a litle over 1 milliamp.
This is also the collector current and perfectly acceptable.
I wonder if there is not a typo with the figures, for example is there a missing negative sign or has someone mixed up Vc and Ve?
What if it is collector is 4V above the base? Or I should say the base-collector is highly reverse biased? Any thing will happen?Studiot said:There is nothing whatsoever wrong with the collector being only 0.3 volts above the base.
When collector is negative with respect to base mean that we forward base-collector?Studiot said:In fact in some circuits in saturation the collector could be taken below the base (ie negative with respect to the base). This condition is called saturation and is what is required in a switching transistor.
The collector - emitter voltage of the type of transistor I talk about here will be about 0.2 volts ie the collector will be at +0.2volts. The base will still be at +0.7 volts.
What if it is collector is 4V above the base? Or I should say the base-collector is highly reverse biased? Any thing will happen?
When collector is negative with respect to base mean that we forward base-collector?
So do you mean that 'Vb-Vc is less than 0.5V' does not mean anything in an active mode of transistor?
I mean Vb=+0.7V, Vc=+100V, and Ve=0Studiot said:What if it is?
Vb-Vc is less than +0.5V mean the collector is at a lower voltage than the base, correct?Studiot said:No it means that 'Vb-Vc is less than -0.5V' since the collector is at a higher voltage than the base.
Studiot said:Physicists are interested in how a transistor works from the point of view of junctions, cariers, holes elctrons etc.
Electrical engineers are not really interested in this but want a model that allows them to predict quantities of interest to create useful circuit configurations.
Which are you interested in?
You appear to be saying that IC = β. IBOutrageous said:Given Vbe=0.7V
Vb=0.7V
Ve=0
Vc=5.0V
Ib=0.45μA
Ic=100Ib
I am, for the reason outlined. With VCE=5 V, it is almost a certainty that the transistor is not in the saturated region of operation.Outrageous said:So do you mean that the transistor is operating in active mode for the question post #9 ?
Studiot said:I do not believe that the circuit arrangement you showed in post#9 will lead to the voltage values etc you listed.
Studiot said:Can you see the difference between your arrangement and my post#4?
There is voltage suppliedOutrageous said:Given Vbe=0.7V
Vb=0.7V
Ve=0
Vc=5.0V
Ib=0.45μA
Ic=100Ib
Will it look okay?
Studiot said:Yes indeed your base resistor as connected will have no voltage across it.
The bias resistors do not determine whether the configuration is common emitter or common collector.
That is determined by the terminal that is common between input and output.
Jony130 said:From your post we can tell one thing. You simply don't understand how NPN transistor work from engineers point of view.
How can any current to flow if the base is connect (short) with emitter?
So from my diagram, the current will not flow through base-emitter even though I connect Vb=+0.7V , instead , the current will straight flow to the earth, correct?
Outrageous said:I asked because I still don't understand . So I must follow your diagram only can get true diagram? I don't know why resistor must connected between base and collector, why not base and emitter.
jim hardy said:2 What does teacher have in mind when (s)he says "operating"?
If that R1-R2 line is connected to positive 5V and the voltages are indeed what you posted,
the transistor is in, or very near, saturation, so it won't have a lot of AC voltage gain.
To an audio person that would appear not operating, but to a logic circuit person it's doing just fine.
Transistors are electronic devices made up of semiconductor materials that can amplify or switch electronic signals. They have three regions - the collector, base, and emitter - that control the flow of current through the device. By applying a small voltage to the base, the transistor can control a larger current between the collector and emitter, allowing it to function as an amplifier or switch.
There are a few ways to test if a transistor is functioning properly. One method is to use a multimeter to measure the resistance between the collector and emitter, and then between the base and emitter. If the resistance between the collector and emitter is low and the resistance between the base and emitter is high, the transistor is likely functioning correctly. Another method is to use a circuit to test the transistor's amplification or switching abilities.
Some common signs of a malfunctioning transistor include no output or a distorted output in an amplifier circuit, a lack of response or incorrect response in a switching circuit, and excessive heat or smoke coming from the transistor. Additionally, if a transistor is physically damaged or has a burned-out appearance, it is likely not functioning properly.
The lifespan of a transistor can vary depending on its usage and environmental factors. However, on average, transistors can last for tens of thousands of hours of use. Factors that can affect the lifespan of a transistor include voltage and current levels, temperature, and the quality of the materials used in its construction.
In most cases, transistors cannot be repaired once they stop functioning. However, they can be replaced with a new one. When replacing a transistor, it is important to ensure that the new one has the same specifications and is compatible with the circuit it is being used in. In some cases, a malfunctioning transistor may also be a sign of an underlying issue with the circuit, so it is important to troubleshoot and address any potential problems before simply replacing the transistor.