Good John not many people remember this. A backwards transistor has 0 Vsat and makes a good chopper switch. This transistor had an ft of 4Mhz hardly RF.
Yes, when I first joined Plessey Semi in the UK in '63, they were just starting up a planar line licenced from Fairchild and went straight in with the '702 and a lot of ECL MIL (flatpack) parts. I think they bought the whole plant from Philco. ? anybody remember?
They still had the old acid etch line (mechanical timers, acid and god knows what squirting everywhere! Nightmare!!
Anyway, one device that still sold at a premium was a silicon symetrical device used as a chopper. In fact I prototyped (although I didn't really know what I was doing!) an "op-amp" using input and output choppers and AC gain to make a very respectable DC moving coil meter amplifier.
Scott - agreed about the trolls; difficult to resist with such mis-information.
Cliff (getting older by the day.)
Wow 1963, you must be of the Barrie Gilbert vintage. For me it's the big 60 on Monday.
Barrie was at Mullard in Southampton and I used to visit him there - I was just a young oik, so I doubt if he would ever remember me.
702s were a real pig to wafer test. In those days we had only semi-automatic wafer probers with individual wired probes, so no performance boards. Just a kludge of stuff trying to stop the DUT from oscillating, which it usually did due to the process being all over the place. I mean, step and repeat was MECHANICAL!!, with the camera on a few tons of concrete to try and damp the vibrations.
Kids these days, don't know what ......
Cliff, 66 and rising
702s were a real pig to wafer test. In those days we had only semi-automatic wafer probers with individual wired probes, so no performance boards. Just a kludge of stuff trying to stop the DUT from oscillating, which it usually did due to the process being all over the place. I mean, step and repeat was MECHANICAL!!, with the camera on a few tons of concrete to try and damp the vibrations.
Kids these days, don't know what ......
Cliff, 66 and rising
I used to test complete 702's and 709's at Friden in 1966. We built a test analyzer that Fairchild published as a schematic at the time. I was in charge of 100's of units, tested them all, myself. I had technicians that worked for me, but this was delicate work. Learned lots of good things.
You would be surprised, I'll see Barrie on Saturday and ask him. Did you get a chance to see the IEEE Spectrum article? They even got some pictures of him as a teenager with a soldering iron in hand?
I got it today, installed. User interface is... hmmm.... very specific. Let's get used to it, then I will tell how convenient it is.
Cliff
They bought a lot of equipment from several companies, with one being Delco, out of St.Louis. Delco made some really good transistors for the Consumer Market. GMC, as we all know, really screwed them up. As Ford has done with Philco. Car Companies>>>>>>>>>>>>>>>>>>>.
No the MPS404 and MPS404A's were not made to be used as choppers. But I am sure someone used it for it. But they were made to be silicon replacements for the 2N404 and 2N404A.
Scott the 2N404 and 2N404A's, were just real good and stable Ge transistors. Most Ge transistors had low ft ratings, until the 2N13XX series.
There were other Ge that had good ft prior to the 2N13XX series. But they proved to be less stable and reliable.
I have a sheet scanner and copier, so I can not scan the book. But I will go to Office Depot and copy it. And scan it through, maybe from that, you get can get a look see at it.
It is nice to know that there is someone a little younger than me there, Cliff.
As you all know Nelson Pass is catching up to us. Soon he will be moving at a lighting fast 4 miles per hour.
Take Care
Ivey
They bought a lot of equipment from several companies, with one being Delco, out of St.Louis. Delco made some really good transistors for the Consumer Market. GMC, as we all know, really screwed them up. As Ford has done with Philco. Car Companies>>>>>>>>>>>>>>>>>>>.
No the MPS404 and MPS404A's were not made to be used as choppers. But I am sure someone used it for it. But they were made to be silicon replacements for the 2N404 and 2N404A.
Scott the 2N404 and 2N404A's, were just real good and stable Ge transistors. Most Ge transistors had low ft ratings, until the 2N13XX series.
There were other Ge that had good ft prior to the 2N13XX series. But they proved to be less stable and reliable.
I have a sheet scanner and copier, so I can not scan the book. But I will go to Office Depot and copy it. And scan it through, maybe from that, you get can get a look see at it.
It is nice to know that there is someone a little younger than me there, Cliff.
As you all know Nelson Pass is catching up to us. Soon he will be moving at a lighting fast 4 miles per hour.
Take Care
Ivey
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Wavebourn
So, it arrived and working. You got to tell me how good it is; once you get to understand it fully.
If is good, and not too big. Email me a copy, and I'll settle the matter with its owner; Nigelwright7557.
Nigel is a guitar player, like I am. Only my fingers do not move fast as before. So I play a little slower now.
Take Care
Ivey
So, it arrived and working. You got to tell me how good it is; once you get to understand it fully.
If is good, and not too big. Email me a copy, and I'll settle the matter with its owner; Nigelwright7557.
Nigel is a guitar player, like I am. Only my fingers do not move fast as before. So I play a little slower now.
Take Care
Ivey
Ivey, I don't want to be too critical, BUT the data sheet says that these specific devices were made for choppers. Also, what do you do with Vbe? It is not compatible with Ge.
Please understand that I worked with Ge too, at a design level, including the 2N404.
The MPS404A MIGHT be a crude replacement for the 2N404, but not an exact one.
Please understand that I worked with Ge too, at a design level, including the 2N404.
The MPS404A MIGHT be a crude replacement for the 2N404, but not an exact one.
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Delco did indeed make interesting devices. In 1966, we started using the DTS-423 for switching power supplies. It is a 400V power device and this series and its cheaper cousin, the DTS-413. Motorola made a clone, later, and this became the output devices for Carver's Phase Linear 700.
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John
Yes, Delco made and designed some really good items. I once had a 27 page circuit handbook that they published in 1965, that included only hifi power amplifiers. I loan it a person who never returned, which only confirms my rule on never loaning out my publications.
I only have one of their designs left. I am looking at it now, It is a 50watt hifi BJT power amp, using DTS-107 transistors. This design came out long before the RCA 70watt design, that became so popular.
No John, you are not being critical, I went on the internet and check out what you are saying. I saw also, what Motorola had done, they id the transistor as a chopper.
Really burns my butt.
But I when post the inform on the forum. You'll see it, and you will not believe your eyes.
It appears they will do anything for a dollar.
So tomorrow, I'll get started on it.
Take Care
Ivey
Yes, Delco made and designed some really good items. I once had a 27 page circuit handbook that they published in 1965, that included only hifi power amplifiers. I loan it a person who never returned, which only confirms my rule on never loaning out my publications.
I only have one of their designs left. I am looking at it now, It is a 50watt hifi BJT power amp, using DTS-107 transistors. This design came out long before the RCA 70watt design, that became so popular.
No John, you are not being critical, I went on the internet and check out what you are saying. I saw also, what Motorola had done, they id the transistor as a chopper.
Really burns my butt.
But I when post the inform on the forum. You'll see it, and you will not believe your eyes.
It appears they will do anything for a dollar.
So tomorrow, I'll get started on it.
Take Care
Ivey
With the greatest respect I cannot let this pass without comment. It is my understanding that Great Britain and the USA agreed an exchange of information on jet technology towards the end of the war. Great Britain gave the US her secrets...... and got nothing in return.
Who should feel aggrieved?
The Me 262 influenced the designs of post-war aircraft such as the North American F-86 and Boeing B-47.
Messerschmitt Me 262 - Wikipedia, the free encyclopedia
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