TTL-ECL translator input/output

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Katie_EE

Joined Apr 8, 2010
14
Hello,

So i am attaching the problem that i am having a difficult time figuring out.

I am also attaching my hand drawn schematics and some calculations. I have gotten as far as determining the reference voltage. But i am confused as to how to determine the input/output voltages...
 

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Ron H

Joined Apr 14, 2005
7,063
You have to understand the differential amplifier to understand this.
When A and B are low, Ie(Q1)=(VR-Vbe(on))/RE. QA and QB are off.
When V(A) is high (>VR), then QA is on, and Q1 is off. Ie(QA)=(V(A)-Vbe(on))/RE.
With V(B)>VR, you get the same results, since QA and QB are in parallel. If both A and B are high, the current will be the same (assumes Vbe(on) is constant, independent of current).
Since you are ignoring base currents (a good approximation in this case), Ic=Ib.
You should be able to calculate output levels from this information.
 
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