# Search results

1. ### Highpass filter

Can't believe it. Can't believe how blind I was.. Offcourse. I mean, I know this, I was just blinded somehow. Too much thought in your head can make you dumb enough to not see the truth. It is just an ordinary HPF! Thank you, Genji! Thanks, Jony! Thanks, Berkeman!
2. ### Highpass filter

Basicaly I stated that when the polarity is reversed the HPF will act as a HPF, but for V- (Looking at a sine wave this V- would be the minimum voltage)
3. ### Highpass filter

Oh, so now as I think of it, "and the output voltage polarity" that might be the case. Normaly this would mean that when the signal shifts polarity, the output voltage will fall(because it forms Low Pass filter) but I think V+ decreasing is like to say the negative voltage is increasing and this...
4. ### Highpass filter

But isn't the point of HPF that if the frequency decrease, Xc will increase and more voltage will fall across the capacitor and progressively less across the resistor which results in a progressively decreasing amplitude of the output signal. Thus HPF won't pass signals below the cutoff...
5. ### Highpass filter

So I wanted to make something clear. I really posted too much threads this week, but that's for the purpose of learning. So a CE Amplifier has a blocking capacitor which together with the input impedance forms a high pass filter. But what I think is this filter is a high pass one only when the...
6. ### Coupling capacitor's value

Thanks once again!
7. ### Coupling capacitor's value

Thanks! And the input resistance is given by R1||R2 + the transistor's input resistance(Ube/Ib)?

Thanks!
9. ### Coupling capacitor's value

I found this in a site called "Learningaboutelectronics" and it says I can use this table to choose a coupling cap for my frequency needs. This sure solves some of my problems, but I need to know how they got these values.
10. ### Coupling capacitor's value

Are there any particular formulas?
11. ### Coupling capacitor's value

How do I determine the value of a blocking capacitor for say this circuit: What I mean is, sure Cin must behave like a short circuit at working frequency, but something tells me there is more to the choice of a coupling capacitor than this.

13. ### Matched biasing transistor

Okay, I understand now. My thanks to all for the help!
14. ### Matched biasing transistor

Okay, Jony130, I've looked at your loop rule equations, and I understand it, but isn't it too long and complicated to use it for setting up the bias? I mean, sure there must be an easier way. Say if Vbe=0,7V, Ve=1V, Vcc=20V, the voltage we need at the collector node of Q1 will be Ve + Vce(sat)...
15. ### Matched biasing transistor

Thank you! I've got one more question if you don't mind. I don't get how this circuit can compensate heat. I mean I believed I do, but things got complicated. What I know is that when temperature increases, Ic1 will slightly decrease the collector voltage. This will reduce the potential...
16. ### Matched biasing transistor

This is where I come from. I made my assumptions, figured out how I can calculate the resistors and now I ask if my way is correct.
17. ### Matched biasing transistor

In my textbook, this circuit can be done with or without adding an emitter resistor which in this case is 180ohms. I first did the calculations if there is no such resistor and then if there is. See, this is the variation of this circuit without the 180ohm resistor. And I ask if this is the way...
18. ### Matched biasing transistor

I have a few questions about the circuit above. 1.This is an ordinary CE amplifier, which uses current mirror to provide temperature stabilization and bias for Q2, right? 2. Like Collector feedback bias and Voltage divider bias, this is just another way of biasing a transistor to provides...
19. ### The true meaning of voltage drop

I can imagine that more resistive materials offer more resistance for the charge to flow through and as a result a greater energy is required to get the electrons through this material. And this greater energy will come from greater potential difference between the ends of this resistive...
20. ### The true meaning of voltage drop

I have read enough similar stuff to know if I am right or wrong. As I said, Voltage, or the potential difference is what gives the electrons potential energy. Once the charges gain this energy, they would start flowing towards the high potential, changing this energy to kinetic energy, which...
21. ### The true meaning of voltage drop

Im not ignoring your answer, but I don't quite get why I should consider the power dissipation. Can you give more in depth example or explanation?
22. ### The true meaning of voltage drop

Okay, I view it this way: It takes electrical energy to get current through a resistor. The more the resistance the more energy it is required to support electron flow. The more the resistance the more potential difference you need to apply across it. When we aply voltage across a circuit with...
23. ### The true meaning of voltage drop

Oh, so from here comes my second confusion that current can increase the voltage drop via the formula V=IxR when in reality it's not the increased current that causes voltage drop, its the voltage across R that caused such a current to flow. But as you said we like to imagine that current can...
24. ### The true meaning of voltage drop

Okay. I now understand that Voltage drop unlike current, or voltage, or resistance, is not a physical property, but rather a way to say, that if you have a circuit with a resistor and you suddenly increase the resistance of that resistor, the current will decrease and you must apply aditional...
25. ### The true meaning of voltage drop

What I understand - Voltage drop is the loss of potential energy in resistors duo to their resistive nature. You increase the resistance - you increase the voltage drop. Not sure though why increasing I will increase the voltage drop. But that's not the question. The question may have routes in...
26. ### The true meaning of voltage drop

Not in that sense. I know that V=IxR. I don't understand the physical process behind it.
27. ### The true meaning of voltage drop

This is it. When Hfe increases, Ic increases and so does Ie and the drop across RE also increases, making the emitter more positive and you know how the feedback works from there on. Similar thing is when in a voltage divider the output falls below a certain level and there is not enough voltage...
28. ### The true meaning of voltage drop

In CE amplifiers with negative feedback I can't understand what it means that the emitter becomes more positive (when hfe increases and VE increases with it). Does it mean that there is less negative charge after the emitter resistor (going from ground to Vcc) and the emitter feels some positive...
29. ### Dynamic resistance

But both static and dynamic resistances are physicaly the same thing - the electrons trying to make their way through the semiconductor material, colliding with it's atoms and slowing down. Right? That's the internal resistance. And in diode there is this resistance and the resistance which the...
30. ### Dynamic resistance

I'm studying semiconductors and i might need a little help with some questions: First the dynamic resistance is the internal resistance of the diodes , but it's called dynamic because it isn't constant, right? Does all semiconductors, pure and doped, have internal/dynamic resistance? The...

Ok, thanks!

34. ### Mutual inductance

Thank you! The analogy with Newtons third law was great. So we expect those two opposite magnetic fields to ballance each other?
35. ### Battery and U

And U is the EU version of V. Both are Voltage
36. ### Battery and U

Also current I is a flow of electrons in one dirrection coused by a potential difference between 2points (in our case A and B). Voltage is also called potential. The faster the electrons the bigger is the heat and light and magnetic field generated. The bigger the potential difference- the...
37. ### Battery and U

What voltage is: Imagine 2 atoms divided by a distance. Atom A and atom B. Atom A looses some of the electrons therefore it becomes more positive(the positive charge of the protons becomes less compensated). Its electric field becomes stronger. Now you should know that every atom has a positive...
38. ### Circuit analysis

Isnt that right mates?
39. ### Circuit analysis

Since both currents unite at the 20k resistor, then u got 240k.80k/320k + 20k= 80000ohms V/Rtotal= 0.006amps net current. From there on u get that 120volts fall at the 20k resistior, and the current through the 60k+180k branch is 0.0015amps. From there the rest current sjould be 0.0045amps
40. ### Battery and U

Becouse the voltage U gets divided between the resistors and so if you have two resistors and 4 volts battery, the voltage gets divided between the two resistors. And so you can have 2volts on one resistor and 2 on the other. Or 3 on one resistor and 1 on the other. It depends entirely on the...
41. ### Mutual inductance

Homework Statement We have coil connected to dc supply and a secondary coil connected to load. We cross the secondary coil with the primary and emf of mutual inductance is induced at that verry moment. Then the induction stops for there is no more change in the flux. However, if an emf is...
42. ### Back electromotive force

Thats right, in inductors back emf is coused by Self induction, which is another type of Electromagnetic induction and it appears only when the crossed by its own magnetic lines. However here we are talking about coils moving in a magnetic stator which is the verry basic type of electromagnetic...
43. ### Back electromotive force

That would be true if the magnetic fields of the coils were constant. Then once the emf would support the source V, once they would oppose its current. Lets say it like this: In generators the magnetic field that the stator creates is constant(it always points in one dirrection). When in our...
44. ### Back electromotive force

Yes, he means indeed Lenzs law. Ya see, the reason for induced emf in the verry basic physical way is (atleast as i understand it) is that when magnetic lines cross the coil, they kinda zap or push the electrons from the atoms there in a certain dirrection that depends on the direction that...
45. ### How electric fields store energy in a capacitor

If you know what atom is, an atom has a core made of protons, hold together by the weak nuclear force.These protons have positive chage and that charge attracts electron(wich have negative charge) that began orbiting around the core. Every electron attracted makes the core less attractive, A...

Uhh.. what?
47. ### How electric fields store energy in a capacitor

"The charge stays the same" and since it is the same, that means that both plates still hold the same potential difference( one plate is still more negative than the other and the other still more positive, and when u connect them current will flow until both plates are at the same potential aka...
48. ### How electric fields store energy in a capacitor

Actualy about c, i think that the distance and attraction force takes part only in charging, and it bassicaly stores more or less charge depending on the distance between the plates. Already charged to some voltage, and since we said that the charge remains nearly the same, when u connect the...
49. ### How electric fields store energy in a capacitor

b: If you mean the electric field between the plates- yes it changes with the distance. When u separate them further apart, the fistance between them is greater and the force of attraction weakens. You can see that fro coloumbs law where F=q1.q2/4p.E.r*2 where r is the distance between two...
50. ### Do motors have some voltage drop across them

Yes it is related. If you hold the load is increased the rotation per minute is decreased and now the coil rotates in the stator magnetic field slower. And from what i consider to be truth: from the formula of em induction E= ^f/^t x n; V it seems that when u decrease the rate of rotation that...