4 ms·

The Transistor (2009) [video]

38 points by olalonde 4y ago

mannykannot 4y ago
I believe this video contains is mistaken in its claim that, in the absence of a base current, PNP transistors (unlike NPNs) freely conduct current between emitter and collector, and that an increasing base current restricts this? IIRC, both types have a high impedance when unbiased, which is reduced as the base current increases, and the only operational difference is the polarity of the voltages for normal operation.
- greenbit 4y ago
  Polarity of the current, too. You have to pull current out of the base of a PNP transistor to get C-E current. If you pull the base of an NPN toward ground, that shuts down the C-E current, but if you pull the base of a PNP toward ground, that turns the C-E current up. Maybe they conflated grounding the base with "absence of base current"?
  - mannykannot 4y ago
    The direction of the currents simply follows from the polarity of the voltage in each case, but this section of the transcripts shows the presenter of the video is talking about the change of magnitude of the collector current in response to a changing base current: 6:02 an NPN bipolar is like a switch which is normally open. it won't conduct until a current is applied at its base terminal. PNP types on the other hand act in the opposite way they reduce the flow in relation to their base current.
readthenotes1 4y ago
Oof. I really wished my newsreader could warn me of an impending commercial video behind these links:(
8bitsrule 4y ago
A good intro in 9 minutes. Good to see the mention of two transistors invented long before Bell Labs got around to it. (Similarly, Oleg Losev was working on LEDs and solid-state electronics back in the 1920s ... publishing 43 papers, all 'overlooked' ... so we didn't have to wait for Roswell after all ;-)
helsinkiandrew 4y ago
Colin Cunningham's YouTube page has a list of the playlists of videos he's made on his own channel and Make and AdaFruit all with traces of his unique style: https://www.youtube.com/@CollinMel https://www.youtube.com/@CollinMel He's made some Macro Lens videos most recently, including this of a sponge: https://www.youtube.com/watch?v=t_CQzkj4Le0&list=PLPeWuN4wB6ev1_ZjazVbIc0tzw7WEYBGH&index=3 https://www.youtube.com/watch?v=t_CQzkj4Le0&list=PLPeWuN4wB6...

38 points by olalonde 4y ago

I believe this video contains is mistaken in its claim that, in the absence of a base current, PNP transistors (unlike NPNs) freely conduct current between emitter and collector, and that an increasing base current restricts this? IIRC, both types have a high impedance when unbiased, which is reduced as the base current increases, and the only operational difference is the polarity of the voltages for normal operation.

greenbit 4y ago
Polarity of the current, too. You have to pull current out of the base of a PNP transistor to get C-E current. If you pull the base of an NPN toward ground, that shuts down the C-E current, but if you pull the base of a PNP toward ground, that turns the C-E current up. Maybe they conflated grounding the base with "absence of base current"?
- mannykannot 4y ago
  The direction of the currents simply follows from the polarity of the voltage in each case, but this section of the transcripts shows the presenter of the video is talking about the change of magnitude of the collector current in response to a changing base current: 6:02 an NPN bipolar is like a switch which is normally open. it won't conduct until a current is applied at its base terminal. PNP types on the other hand act in the opposite way they reduce the flow in relation to their base current.

readthenotes1 4y ago

Oof. I really wished my newsreader could warn me of an impending commercial video behind these links:(

8bitsrule 4y ago

A good intro in 9 minutes. Good to see the mention of two transistors invented long before Bell Labs got around to it. (Similarly, Oleg Losev was working on LEDs and solid-state electronics back in the 1920s ... publishing 43 papers, all 'overlooked' ... so we didn't have to wait for Roswell after all ;-)

helsinkiandrew 4y ago

Colin Cunningham's YouTube page has a list of the playlists of videos he's made on his own channel and Make and AdaFruit all with traces of his unique style: https://www.youtube.com/@CollinMel https://www.youtube.com/@CollinMel He's made some Macro Lens videos most recently, including this of a sponge: https://www.youtube.com/watch?v=t_CQzkj4Le0&list=PLPeWuN4wB6ev1_ZjazVbIc0tzw7WEYBGH&index=3 https://www.youtube.com/watch?v=t_CQzkj4Le0&list=PLPeWuN4wB6...