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  1. R

    Nodal Analysis of a Circuit

    Then why do you mark "ref" where the 1,4,2 ohm resistors come together? Charge may or may not flow. Current is already flowing. "Current flow" means "charge flow flow", which is wrong and confusing. You should not be wondering which direction the current has. Do the algebra and let the...
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    Reactance Question

    Reactance is not imaginary resistance (whatever that is) or any other kind of resistance. Reactance and resistance both inhibit current, but they do it by two different ways. Resistance inhibits current by converting the charge energy density into heat, thereby causing an energy loss, which...
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    Reactance Question

    Wrong, the resistance does not change with frequency. The impedance changes, but the resistance remains the same. Ratch
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    Gone on vacation

    I am back. Ratch
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    Gone on vacation

    I will be absent from this forum for up to two weeks starting tonight while visiting a friend. Ratch
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    Transistor hfe

    That transistor has a minimum beta of 400. Therefore each transistor will have at most a base current of 5/400 = 12.5 milliamps. Six of those transistors will make a total base current of 75 milliamps. I did that calculation previously. Who cares if the maximum base current of each transistor...
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    Transistor hfe

    Don't get hung up on formulas. Understand what you are doing and then calculate the values you require. Ratch
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    Transistor hfe

    If the base-emitter voltage stays the same, you do not have to change R7. Does 25 ohms make sense? 5 volts is the maximum base-emitter voltage, not what you use for nominal design. What is the maximum current you desire through the 7812? What are you assuming for the base-emitter voltage? Ratch
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    Transistor hfe

    Yes, three watts or greater. I don't think 3 watts is a standard size. I think 4 watts is, but I could be wrong about that. Since the transistors are darlingtons, 0.86 * 1.2 = 1 volt sounds a little low. I would assume 1.5 volts at least. The wattage for the 6 emitter resistors should be 5...
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    Transistor hfe

    It really should be twice the calculated wattage or 20 watt to conform to good practices. I imagine the 7812 has internal circuitry that limits the current to one amp. The specs say the quiescent current of the 7812 is 5 milliamps. I don't know whether this current comes from the input or...
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    Transistor hfe

    You can't make a BJT (bipolar junction transistor) by connecting two diodes back to back. There is a lot more to a BJT than that. See below for discussion of R7. Transistors need a base current like a city needs a sewage system. They are both waste quantities. You specified 0.5 watts for...
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    Transistor hfe

    I think both you and several responders to this thread are in need of an adjustment in perceiving how a BJT transistor works. First of all, a BJT is not a current amplifier, beta is not the current amplification factor, and you do not control or drive the transistor with current. Without going...
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    Transistor hfe

    You might want to look at post #2 in this link. http://www.electro-tech-online.com/threads/bullet-proof.146490/#post-1240701 Ratch
  14. R

    tuned (tank) circuit, oscillator, Q

    Yes, you are correct. I was thinking of how often the energy in L and C considered separately reach a peak or zero, which is twice per hertz. However, those points are 90° apart for L and C. Ratch
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    Differential amplifiers - why amplify the difference?

    You seem to have a problem with an amplifier's functionally, and how it is implemented. Lets discuss a single-input amplifier first. Within the amplifier's frequency range, both noise and signal are amplified. There is no way to distinguish between noise and signal if both are in the same...
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    Discharge time of 2 capacitors in parallel

    Voltage is its rating. Value in microfarads is its capacitance value, not rating. What is the capacitor "discharging"? Ratch
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    Differential amplifiers - why amplify the difference?

    You don't have to feed all the output back to the input. Just a fractional amount. An operational amplifier is one big differential amplifier. Look at how useful they are. There is plenty of elementary material on op-amps that you should find interesting. Ratch
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    Discharge time of 2 capacitors in parallel

    Are you talking about the RC time constant? Depending on what kind of capacitor you have, the physical resistance should not be more than a few ohms. How does that compare with the other resistance in the circuit? Is it worth worrying about? If necessary, I can calculate the response of two...
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    Discharge time of 2 capacitors in parallel

    You need to get your understanding of ESR checked and calibrated. ESR is an AC phenomena, and is a measure of the lossiness of capacitor. You need to read and understand the mat4rial in this link. http://my.ece.ucsb.edu/York/Bobsclass/194/References/General/ESR%20of%20Capacitors.pdf Ratch
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    Basic Question concerning what Amps are?

    Why amps? Why not the lack of resistance. If the wire was a superconductor, then no amount of current would produce heat. Ratch
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