25-02-2017, 12:17 PM
I'm certainly behind the comments about ignoring physics and, in the main, text books.
As far as the holes in transistors are concerned, I've been happily ignoring those for over half a century!
Of course, I grew up firmly entrenched in the valve era. If there was ever a design using transistors in Practical Wireless during my schooldays, I can't remember it. Indeed, when they did start appearing a few years later, they promptly moved to a new magazine, Practical Electronics!
Thinking back to my schoolboy studies, I probable learnt the type of metal used for every valve electrode, the chemicals required to produce the emissive material for the cathode and so on. When you think about it, what I really was learning was how to build my own valves! Of course, I lacked the specialised equipment needed and the skills to operate them - not to mention a degree in glass blowing! - so, apart from any casual interest, there wasn't one single phrase in anything I read that was of any practical use whatsoever!
Then, of course, we moved onto transistors, growing 100% pure germanium and silicon, then poisoning it to create P and N types and so on, before finally putting them together in various ways to create PNP and NPN devices. It's strange, but the only physical aspect of transistor construction that had any practical application was never discussed in all these texts, causing much consternation to engineers when presented with battery operated transistor radios for repair that suffered from mains hum!
This, of course, was only a problem with glass encapsulated transistors if the paint got scratched allowing artificial light to fall on the junction - and was quickly resolved by the manufacturers filling the inside of the glass container with an opaque silicon grease.
Photo electric transistors were available, of course - at a high price - but these were presented as having been specially made to be photo sensitive when, in fact, there was just an ordinary transistor inside the clear glass encapsulation which had been modified to include a lens!
One thing that has not been mentioned here that is important to learn is which way up transistors work. No valve can conduct unless its anode is positive with respect to its cathode so there is no such thing as a valve that works 'upside down' (in an electronic, rather than physical sense).
Transistors, however, are different. An NPN transistor mimics a valve in that it conducts with it's collector positive with respect to its emitter whereas a PNP type conducts with it's collector negative with respect to its emitter. To anybody brought up in the valve era and attempting to grasp this new technology it was confusing as all the early transistors were PNP types and the battery positive terminal was usually connected to the chassis or earth line. Even the sight of all the electrolytics which appeared upside down compared to 'normal' added to the strangeness of the new circuits.
Analogue multi-meters don't 'do' negative, unlike their modern DMM cousins which just stick a negative sign in front of the number so you even had to reverse the test leads to take any measurements!
Still, we all survived the transition ...
As far as the holes in transistors are concerned, I've been happily ignoring those for over half a century!
Of course, I grew up firmly entrenched in the valve era. If there was ever a design using transistors in Practical Wireless during my schooldays, I can't remember it. Indeed, when they did start appearing a few years later, they promptly moved to a new magazine, Practical Electronics!
Thinking back to my schoolboy studies, I probable learnt the type of metal used for every valve electrode, the chemicals required to produce the emissive material for the cathode and so on. When you think about it, what I really was learning was how to build my own valves! Of course, I lacked the specialised equipment needed and the skills to operate them - not to mention a degree in glass blowing! - so, apart from any casual interest, there wasn't one single phrase in anything I read that was of any practical use whatsoever!
Then, of course, we moved onto transistors, growing 100% pure germanium and silicon, then poisoning it to create P and N types and so on, before finally putting them together in various ways to create PNP and NPN devices. It's strange, but the only physical aspect of transistor construction that had any practical application was never discussed in all these texts, causing much consternation to engineers when presented with battery operated transistor radios for repair that suffered from mains hum!
This, of course, was only a problem with glass encapsulated transistors if the paint got scratched allowing artificial light to fall on the junction - and was quickly resolved by the manufacturers filling the inside of the glass container with an opaque silicon grease.
Photo electric transistors were available, of course - at a high price - but these were presented as having been specially made to be photo sensitive when, in fact, there was just an ordinary transistor inside the clear glass encapsulation which had been modified to include a lens!
One thing that has not been mentioned here that is important to learn is which way up transistors work. No valve can conduct unless its anode is positive with respect to its cathode so there is no such thing as a valve that works 'upside down' (in an electronic, rather than physical sense).
Transistors, however, are different. An NPN transistor mimics a valve in that it conducts with it's collector positive with respect to its emitter whereas a PNP type conducts with it's collector negative with respect to its emitter. To anybody brought up in the valve era and attempting to grasp this new technology it was confusing as all the early transistors were PNP types and the battery positive terminal was usually connected to the chassis or earth line. Even the sight of all the electrolytics which appeared upside down compared to 'normal' added to the strangeness of the new circuits.
Analogue multi-meters don't 'do' negative, unlike their modern DMM cousins which just stick a negative sign in front of the number so you even had to reverse the test leads to take any measurements!
Still, we all survived the transition ...
