Claude,
It sounds like a clunky, clumsy way to distribute power. So if a heating element in a electric oven or a light bulb broke, we would have an electric arc until the arc got shorted?
Sure it does, the equations given prove it. The page was from Gerold W. Neudeck's The Bipolar Jujnction Transistor, by the way.
The energy lost and current in the base is very low because most of the current is shunted to the collector because of the geometry of the BJT. This includes a very thin base, asymmetrical doping, and a Vcc. Vcc is what supplies most current and power in the active region. Vbe is what enables the charge carriers to keep entering the base region where they are swept onto the collector. If it were possible, Ib could be eliminated. But it is inevitable that a small amount of Ib wastage current will be present.
Whichever way you figure it out, the Vbe controls the diffusion which brings charge carriers into the base region where they are sent on to the collector. The base current is not needed, nor is it in the equation for Ic. The base current is a waste charge flow that happens to be proportional to Ic.
No, not after. Vbe is what enables diffusion in the first place. Current drift has nothing to do with this.
The physics also apply to DC and lower frequency. It is wrong to assert that cause and effect cannot be determined at DC or lower frequencies. Diffusion still exists under those conditions. Charge storage does affect the timing of the effects, but it does not affect the cause and effect. I did address that in page 5, posts 49 through 51 in this thread. Did you read it?
We are in the active region at DC or low frequencies. I do recognize that storage charge affects the timing of responses between voltage and current. I showed that earlier in this thread. Sedra and Neudeck use Vbe in their equations to show a causal, not functional relationship.
All the above paragraph has nothing to do with Vbe controlling Ic. Of course AC voltage can exist without current if no capacitance if present.
The only causal current activated device I can think of at the moment is a magnetic amplifier. A LED works well when driven by a current, but like all junction diodes, it is causal voltage activated device which activates the current present within.
Yes, current does not exist without voltage, either internal or external. Voltage represents energy per unit charge, and the charges just are not going to move anywhere without energy to do so.
Ratch
With constant current, the switches are placed across the outlets. A switch closed is the off position. An appliance is plugged into an outlet which is across the switch. An open switch turns the appliance on. All the outlets are in series for a given branch. With CVS, the outlets in a branch are parallelled. If all devices are switched off, all switches are closed. All of these outlets have 0 volts across them, but the current is constant & no power is consumed. You have to reorient your thinking with CCS, as it is the counterpart of CVS.
It sounds like a clunky, clumsy way to distribute power. So if a heating element in a electric oven or a light bulb broke, we would have an electric arc until the arc got shorted?
LED forward voltage does not control the current. The page you copied from Sedra & Smith makes no reference to such a concept.
Sure it does, the equations given prove it. The page was from Gerold W. Neudeck's The Bipolar Jujnction Transistor, by the way.
The junction provides a barrier which the power source must overcome by losing some energy. Just as Id = Is*exp((Vd/Vt)-1), it also holds that Vd = Vt*ln((Id/Is)+1).
The energy lost and current in the base is very low because most of the current is shunted to the collector because of the geometry of the BJT. This includes a very thin base, asymmetrical doping, and a Vcc. Vcc is what supplies most current and power in the active region. Vbe is what enables the charge carriers to keep entering the base region where they are swept onto the collector. If it were possible, Ib could be eliminated. But it is inevitable that a small amount of Ib wastage current will be present.
Physics texts usually use the I-V form, but many refer to the V-I form of the same equation.
Whichever way you figure it out, the Vbe controls the diffusion which brings charge carriers into the base region where they are sent on to the collector. The base current is not needed, nor is it in the equation for Ic. The base current is a waste charge flow that happens to be proportional to Ic.
Your whole crux is that after all diffusion has taken place, strange you never mention drift, the value of Vd attained is what dictates the current.
No, not after. Vbe is what enables diffusion in the first place. Current drift has nothing to do with this.
If you insist on ignoring transients & staying in dc, then it is pointless to argue. In dc & low frequency operation, it is impossible to ascertain which mechanism accounts for this or that. Only pulsing quickly & measuring on a scope can give insight into what is happening.
The physics also apply to DC and lower frequency. It is wrong to assert that cause and effect cannot be determined at DC or lower frequencies. Diffusion still exists under those conditions. Charge storage does affect the timing of the effects, but it does not affect the cause and effect. I did address that in page 5, posts 49 through 51 in this thread. Did you read it?
To summarize, when bjt is working in conditions where CC model is inadequate, such as high speed, or saturated switch, the only model physicists invoke is charge control. You seem to ignore that model & want to use VC for internal physics, which nobody uses. All Sedra & Smith invoke is the functional relation between Vbe & Ic.
We are in the active region at DC or low frequencies. I do recognize that storage charge affects the timing of responses between voltage and current. I showed that earlier in this thread. Sedra and Neudeck use Vbe in their equations to show a causal, not functional relationship.
You don't even accept that power distribution can just as well be CC or CV. It isn't done because conduction losses are so much higher than insulator losses. Generating full current/variable voltage all the time results in heavier losses than full voltage/variable current. Also, you mentioned that if current is present there has to be a voltage. But the reverse is true as well. In static conditions a superconducting inductor can sustain a current w/o voltage, & a perfect capacitor can sustain voltage w/o current. But with ac, neither can independently exist. An ac wall outlet in the open state cannot have ac voltage w/o ac current. Just ponder on that.
All the above paragraph has nothing to do with Vbe controlling Ic. Of course AC voltage can exist without current if no capacitance if present.
You don't consider current as anything more than the result of connecting a voltage across an impedance. In your mind every current is driven by a voltage. With that frame of mind, current controlled devices don't exist. Every LED maker describes LEDs as current driven, & all LED drivers use constant current using switching a FET with an LED, inductor &catch diode to keep the LED at constant current. Increasing brightness is done by increasing current, with an increase in Vd being incidental.
The only causal current activated device I can think of at the moment is a magnetic amplifier. A LED works well when driven by a current, but like all junction diodes, it is causal voltage activated device which activates the current present within.
I cannot keep harping abut this. If you believe voltage is what drives current, my talking is pointless. Good day.
Yes, current does not exist without voltage, either internal or external. Voltage represents energy per unit charge, and the charges just are not going to move anywhere without energy to do so.
Ratch