[Test-Equipment] Transistor Circuit Design Question

[David]

ECL intended to use a -5.2 volt negative supply is sometimes run on +5
volts (PECL or positive ECL) and +5 volt logic is sometimes used with
a -5.2 volt ECL supply but level shifting is still needed.  The tricky
part is that logic levels are referenced to something and if you mix
logic families which were designed for different polarity supplies,
then noise margins can be compromised.

In your specific case one reason I might *not* run them both on the
same supply is if there was an issue with coupled noise which is
always a possibility in a high resolution multimeter.

On Tue, 26 May 2015 09:34:29 -0400 (EDT), you wrote:

>Hi David,
>
>Okay - thanks so much for the analysis.  I'm not sure if I'll stick with shifting the voltages or just run the entire thing between -5V and 0V as the other David suggests.  I may try your suggestions just to prove it out for my own satisfaction.
>
>Thanks again,
>Barry - N4BUQ