How am I supposed to connect two logic circuits which are not of the same family

Question

Say I have to couple a NOR \$I^2L\$ and an ECL logic circuit, in such a way that the output voltages of the \$I^2L\$ are suitable for ECL use. Let me show you what I mean: I thought adding a voltage divider might do the trick. When we have either A or B high the output of the \$I^2L\$ is 0.2V, the collector-emitter saturation voltage. Using a voltage divider as shown in the image, I can convert this logic zero of 0,2 V to a logic zero of let's say -1,7V( less than Vref) which is the input for the ecl circuit, and will be a logic 0 in terms of the voltages present in the ecl. However, I am not sure how to make a logic 1 using this divider. The first cicruit gives us a logic 1 if both A and B are zero, and in that case the input for the second circuit is just -Vee, a logic zero, not a logic 1. Note that this is just for academical purposes, so I guess there are solutions which are easily grasped.

Answer 1

Maybe use a common-base transistor to buffer current between the positive logic circuit and negative logic circuit, something like this:

^{simulate this circuit – Schematic created using CircuitLab}

It's up to you to find the resistor values that give proper NECL levels at the output. You don't have to be precise, ECL is pretty robust to varying logic levels if you're not trying to get maximum speed from it.