D 15.54 For the ECL circuit in Fig. P15.54, the transistors exhibit VBE of 0.75 V at an emitter current I and have very
high ß
(a) Find VOH and VOL.
(b) For the input at B that is sufficiently negative for QB to be cut off, what voltage at A causes a current of I/2 to flow in QR?
(c) Repeat (b) for a current in QR of 0.99I. Define this value of vA as VIL .
(d) Repeat (c) for a current in QR of 0.01I. Define this value of vA as VIH .
(e) Use the results of (c) and (d) to specify VIL and VIH .
(f) Find NMH and NML. (g) Find the value of IR that makes the noise margins equal to the width of the transition region, VIH -VIL
(h) Using the IR value obtained in (g), give numerical values for VOH, VOL, VIH , VIL , and VR for this ECL gate.
