Author Topic: Some 555-Timer-Dies  (Read 7163 times)

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Offline Noopy

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Re: Some 555-Timer-Dies
« Reply #75 on: November 21, 2020, 07:23:15 pm »
Finally the soviet NE555, the КР1006ВИ1 (KR1006VI1):






You can find a datasheet written by Alfa but I assume the КР1006ВИ1 was built by more soviet manufacturers.
The design is different to any die I have decapped until now.
In the upper right corner of the labeling there are four diodes leading to a long resistor. The string is connected between supply and ground. It looks like the potential between diodes and resistor is used for a kind of biasing in the trigger differential amplifier. That´s something I haven´t seen in any other NE555.

https://www.richis-lab.de/555_36.htm

 :-/O
 
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Offline Noopy

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Re: Some 555-Timer-Dies
« Reply #76 on: April 13, 2021, 06:58:41 pm »




That´s the oldest NE555 I have.




It seems like a silicone mold. It was very hard to remove.
On surface of the die there is something like a protection layer.




The die is quite similar to the newer Signetics NE555 but...




There is one difference. In the older design Q10/Q11 are acting like a darlington transistor. In the newer designs Q10 is connected to ground. In addition Q11 is a current mirror which is not mentioned in the datasheet.
I assume connecting Q10 to ground makes the trigger circuit switching faster but why that current mirror?  :-//


https://www.richis-lab.de/555_6.htm

 :-/O

Online magic

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Re: Some 555-Timer-Dies
« Reply #77 on: April 14, 2021, 07:04:27 pm »
It's nothing special, just additional bias for Q10, perhaps to speed it up or reduce its output impedance or whatever. And grounding its collector enables the comparator to function all the way down to ground like LM358.
 

Offline Noopy

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Re: Some 555-Timer-Dies
« Reply #78 on: April 15, 2021, 03:07:39 am »
It's nothing special, just additional bias for Q10, perhaps to speed it up or reduce its output impedance or whatever. And grounding its collector enables the comparator to function all the way down to ground like LM358.

I assume the grounded collector gives you some more switching speed too. A little more Vce, a little more Ic. A little more Ic, a little faster switching of Q11. What do you think?

Regarding the current mirror: Isn´t it a drawback that the current mirror eats up half of the current which otherwise could switch the next stage with more current (=more speed)?

Online magic

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Re: Some 555-Timer-Dies
« Reply #79 on: April 15, 2021, 06:41:31 am »
Not a problem if total Q11+Q12 current is set appropriately. Some LM358 use this exact scheme on their Q10/Q13, while others have dedicated current sources.

It doesn't seem clear if it's exactly 50% of the current being redirected here.
« Last Edit: April 15, 2021, 06:44:53 am by magic »
 
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Offline David Hess

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Re: Some 555-Timer-Dies
« Reply #80 on: April 16, 2021, 02:49:44 am »
The current mirror allows Q10 to operate at a higher collector current for better performance.

Not a problem if total Q11+Q12 current is set appropriately. Some LM358 use this exact scheme on their Q10/Q13, while others have dedicated current sources.

The datasheet schematics often leave those details out.

Quote
It doesn't seem clear if it's exactly 50% of the current being redirected here.

That depends on the emitter ratios which are only rarely documented.
 
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Online magic

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Re: Some 555-Timer-Dies
« Reply #81 on: April 16, 2021, 06:28:07 am »
That depends on the emitter ratios which are only rarely documented.
Or the collectors ;)

And an example seen in the wild: 75% of input pair current goes to the buffers; this also takes care of the "transconductance reduction" thing.
https://zeptobars.com/en/read/ST-TS321-SOT23-opamp-LM358A-LM324
 

Offline Noopy

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Re: Some 555-Timer-Dies
« Reply #82 on: April 16, 2021, 03:30:18 pm »
Thanks for your explanations.  :-+
I remember the transconductance reduction!  :-+ :)

Offline David Hess

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Re: Some 555-Timer-Dies
« Reply #83 on: April 17, 2021, 04:13:27 pm »
I remember Bob Pease's comment about how they documented emitter area:

Maybe I should explain about the "ranchette.”  The "ranchette" is a unit of area defined as 1/2 pico-acre.  The ranchette is exactly the size of a round emitter 1 milli-inches in radius (well, 0.9983 milli-inch), so it really is handy when dealing with large matched pairs of transistors.
 


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