Re: Tek IC clone possible?
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On the surface, they don;t seem that difficult.? One thing that could be useful is to determine the output R for starters.? For starters, you can add a variable resistor in series with a lead and see when the output drops to 1/2 the voltage.
My guess, too is that you could create an RC divider similar to a scope probe to get an idea of the parasitics especially if the inputs have a fast edge.
Next, you need to get a handle on the logic levels.
They could, for instance be a wierd mix of stuff like TTL inputs and ECL type outputs.? Who knows.
Get the input Z right and the output Z right and the logic levels and you stand a chance.
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--- On Tue, 7/24/12, Fabio Eboli wrote:
From: Fabio Eboli
Subject: Re: [TekScopes] Re: Tek IC clone possible?
To: TekScopes@...
Date: Tuesday, July 24, 2012, 5:54 AM
?
Steve, see the other post, I posted some
diagrams for the two ics I could be interested to replicate.
Is it possible that Tek had an internal sort of standard
for logic functions? In these diagrams seem that
input logic one is something able to drive a transistor
base form ground, as for output seem that logic one
can be something around 1V, at least for the 155-0013.
Fabio.
Steve <ditter2@...> ha scritto:
> --- In TekScopes@..., KeepIt SimpleStupid
> wrote:
>>
>> Not necessarily.?? If you have a block diagram and a description of
>> the device that you want to replace, post it.?? From there, maybe
>> we as a group could suggest what might be able to be used to
>> substitute the internals.
>>
>
> In addition to its logic diagram, you need to look at the circuit it
> is used in.
>
> Because Tek made ICs are single sourced, Tek engineers could rely on
> parameters that are typically "unspecified" as being consistent.
>
> Things such as input and input impedances, pull up resistor values,
> Ft and Miller C of the transistors, etc. would not change as they
> may with different vendors' version of the same logic circuit.
> Hence, in Tek designs you often see analog signals driving inputs or
> outputs driving analog signals which depend on these
> characteristics. Simple substitution of a functionally logic
> equivalent circuit may not operate if these conditions are not
> duplicated, possibly using external components.
>
> The first Tek made ICs of the part numbers you mentioned were
> fabricated on a 200 ohm/square process ¨C Tek's first. This is not a
> very fast process (transistor Ft and switching speed) by today's
> standards. In some cases you may need to slow down output
> transitions to substitute FPGA equivalents.
>
> - Steve
>
>
>
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