The schematic of a current mode logic (CML) inverter is shown in
Fig. 6.12a. The evolution of the node voltages during
DC operating point calculation is shown in Fig. 6.13. Best
results were obtained with
= 3. With ABC 20 iterations were
needed whereas 24 with DBC.
For the other points following in the DC transfer characteristic the required number of iterations is exactly equal (12-18) and hence not shown. The simulated transfer characteristic is shown in Fig. 6.14.
For ABC one gets KA = 20/19 = 1.052 and for DBC KD = 24/21 = 1.1428 which both can be considered close to optimum.
In Fig. 6.12b the current source is realized as a current
mirror. The number of unknowns increases to about 10000 and 48 iterations were
needed using DBC and
= 3. No convergence could be obtained for
ABC.
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