Cheers,
Michael
Cheers,
Michael
Ha.
What exactly is the point of the coil labeled H, anyway? And why is it given a (+) symbol?
The diagram represents a vacuum tube rectifier circuit. Coil H supplies heating power to the rectifier's filament which acts as a source of electrons and therefore as the cathode. The + symbol marks the positive output rail.
Oh! Cool! Thanks!
You youngsters have clean forgotton how toobs work. "H" is for "heater."
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers
Unfortunately a lot of knowledge has been lost, it's true. Didn't a Soviet fighter pilot defect a few decades ago, taking a Soviet supersonic jet with him, with all sorts of EMP-proof vacuum tube electronic controls? :)
Michael
That's a sad rectifier tube, not a sad inductor. It's sad because it knows that there's young whippersnappers out there that can't recognize the schematic symbol for a rectifier tube any more.
-- Tim Wescott Wescott Design Services
The other day, my brother's grandson - don't have one myself yet although I'm well into that age - saw my old portable mechanical typewriter and asked me how it's connected to a computer.
When I start into active devices in the training classes I conduct, I usually begin with vacuum tubes. Besides making the students appreciate how technology developed, I feel that visualizing a stream of tiny electron balls - classical physics is good enough for the purpose - flying through a vacuum from cathode to anode gives them a clear mental image of how it all works. It's further useful at the next step: control of the current flow with a grid. It also has a kind of elegance to it. I go into the maths later.
I was either lucky or unlucky that when I went to tech school in 1970 that tubes and transistors were both being taught. Had to learn both types of circuits.
Not sure who, thinking Ben Franklin that got the electron flow backwards. That gave us electron flow and convencional current flow to remember.
Us regular critters can generally forget about which way the electrons go in a circuit. With complementary devices it almost doesn't matter at all.
However there is a reason thaty silicon NPN transistors are better and germaniun PNP transistors were better. That is more on a molecular level and that's the job of people who work at Onsemi and the like.
Did you tell him about its excellent hacker-proof properties? :)
I thought that the only driver behind the Germanium PNP thing was because point-contact transistors pretty much have to be PNP due to the physics of strained crystals.
-- Tim Wescott Wescott Design Services
I don't know about which is beter,but probably the big reason is to have a negative ground system.
Some impressions I've retained from some 40+ years ago - Ge transistors had lower Vce(sat) than Si. This and the lower Vbe were significant in low-voltage applications. Ge power transistors also had better gain linearty as we approach a device's max current ratings.
Some impressions I've retained from some 40+ years ago - Ge transistors had lower Vce(sat) than Si. This and the lower Vbe were significant in low-voltage applications. Ge power transistors also had better gain linearty as we approach a device's max current ratings.
NPN silicon transistors definitely tend to be better, for the same reason N-channel MOSFETs do: electron mobility in N-type silicon is better than hole mobility in P-type.
I'm pretty sure the same thing applies to germanium.
The very first transistors were point-contact type, though, which worked because when you stress lightly-doped N-type germanium it becomes P-type. However, it only works for PNP transistors.
-- Tim Wescott Wescott Design Services
The commonly available early PNP Ge transistors (CK722, 2N107, etc) were g rown junction devices, not point contact. It was easy to make a PNP by usi ng aluminum or indium to make contact to the n-doped Ge substrate. This wa s not a very reproducible process because the it was dificult to control th e thickness of the base and the doping levels in the emitter and the collec tor. It was the planar diffused process (which could not be made to work w ith Ge) that made Si transistors consistently superior to Ge.
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