TTL-ECL translator input/output

Discussion in 'Homework Help' started by Katie_EE, May 17, 2010.

  1. Katie_EE

    Thread Starter New Member

    Apr 8, 2010

    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...
    Last edited: May 19, 2010
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    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.