I agree with the above two posts.
I guess I see "base current controls collector current" as a useful simplification when applied to a very common first use of a transistor. If this is as far as someone goes it will be sufficient.
I agree that if you teach the diode first (presumably going into detail about the relationship between V and I through the device -- and let's exclude some of the more exciting devices) then you can easily explain transconductance on the basis of what is already assumed knowledge.
Presumably also when discussing the relationship between V and I in the diode you would also have indicated that destructive (to practical devices) currents will floor if the diode is connected to an inappropriate voltage source.
Armed with that, an attentive student would come to the same conclusion about the BE junction of a bjt. If they don't, you point then back to their notes or text and get them to read about diodes again.
Unfortunately, if someone wants a very quick explanation, that's going to take too long and you'll get TL;DR.
Like it or not, many people are exposed to electronics in an order that makes no sense from a teaching perspective. I assist people (in meatspace) in a regular microcontroller user group meeting. There are many there for whom ohms law is a concept for their future self.
In real life is a lot easier to see people's eyes glaze over. And outside the lecture theatre it's a bit rich to consider that their problem.
If they know that they have a small current available from their microcontroller output pin and their relay requires a higher current (and let's assume they don't need to be told this) then they are not going to want to sit through Vbe, diffusion of electrons and transconductance before finally getting to the practical "I need a resistor of about this value to allow a small but sufficient current into the base in order for a larger current to be switched through the transistor to pull in the relay.". I'd prefer to leave them with sufficient knowledge to tackle this task themselves next time and I already have the burden of introducing them to ohms law and inductance. If the simple practical task of driving a relay is not going to become the entire topic for the evening, it has to be done at a high level.
I really don't want to have to say "you apply a voltage, but don't apply a voltage, apply a current. But you can't apply a current, you apply a voltage with a series resistor and it will create a potential divider with the BE junction and the right voltage will appear there to enable the current to flow. How do we calculate it? Well let's assume the variable Vbe is actually a constant..."
I have had no problem with people understanding that a particular view of operation is a simplification that won't hold true if you push it too far.
However I've seen too much information (especially if it seems superfluous at the time) cause people to lose interest and drift off.
To turn this back to the topic, I'm not sure that presenting "Ib controls Ic" to the OP would have been the right thing (in fact I would assume the contrary). I assume he would be asked questions based on the information presented in lectures he has missed, which I further assume was in more see detail than I would present to someone who wants something in 5 minutes or less.
I was just assuring the person who linked to the video that while it may not have been appropriate (but who knows) it was simply presenting a simplification that some people don't like, but that others are OK with.
And then I was pointing out that any explanation that doesn't include all the details is necessarily wrong. However wrong does not imply useless (e.g. Newtonian physics for cases most people see in their daily lives). And while I agree with the "simpler, but not too simple" quote, I disagree with others on what "too simple" means.
I guess I see "base current controls collector current" as a useful simplification when applied to a very common first use of a transistor. If this is as far as someone goes it will be sufficient.
I agree that if you teach the diode first (presumably going into detail about the relationship between V and I through the device -- and let's exclude some of the more exciting devices) then you can easily explain transconductance on the basis of what is already assumed knowledge.
Presumably also when discussing the relationship between V and I in the diode you would also have indicated that destructive (to practical devices) currents will floor if the diode is connected to an inappropriate voltage source.
Armed with that, an attentive student would come to the same conclusion about the BE junction of a bjt. If they don't, you point then back to their notes or text and get them to read about diodes again.
Unfortunately, if someone wants a very quick explanation, that's going to take too long and you'll get TL;DR.
Like it or not, many people are exposed to electronics in an order that makes no sense from a teaching perspective. I assist people (in meatspace) in a regular microcontroller user group meeting. There are many there for whom ohms law is a concept for their future self.
In real life is a lot easier to see people's eyes glaze over. And outside the lecture theatre it's a bit rich to consider that their problem.
If they know that they have a small current available from their microcontroller output pin and their relay requires a higher current (and let's assume they don't need to be told this) then they are not going to want to sit through Vbe, diffusion of electrons and transconductance before finally getting to the practical "I need a resistor of about this value to allow a small but sufficient current into the base in order for a larger current to be switched through the transistor to pull in the relay.". I'd prefer to leave them with sufficient knowledge to tackle this task themselves next time and I already have the burden of introducing them to ohms law and inductance. If the simple practical task of driving a relay is not going to become the entire topic for the evening, it has to be done at a high level.
I really don't want to have to say "you apply a voltage, but don't apply a voltage, apply a current. But you can't apply a current, you apply a voltage with a series resistor and it will create a potential divider with the BE junction and the right voltage will appear there to enable the current to flow. How do we calculate it? Well let's assume the variable Vbe is actually a constant..."
I have had no problem with people understanding that a particular view of operation is a simplification that won't hold true if you push it too far.
However I've seen too much information (especially if it seems superfluous at the time) cause people to lose interest and drift off.
To turn this back to the topic, I'm not sure that presenting "Ib controls Ic" to the OP would have been the right thing (in fact I would assume the contrary). I assume he would be asked questions based on the information presented in lectures he has missed, which I further assume was in more see detail than I would present to someone who wants something in 5 minutes or less.
I was just assuring the person who linked to the video that while it may not have been appropriate (but who knows) it was simply presenting a simplification that some people don't like, but that others are OK with.
And then I was pointing out that any explanation that doesn't include all the details is necessarily wrong. However wrong does not imply useless (e.g. Newtonian physics for cases most people see in their daily lives). And while I agree with the "simpler, but not too simple" quote, I disagree with others on what "too simple" means.
