Fanout Driver Limit Three-Row Scan - Electronic Circuits XI: Transistor Switching and Device Regions Step by Step

Driver margin is the current limit minus the same six-base demand. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Two-ampere driver limit cannot feed six bases

6 bases at 1/2 A each total 3 A. Driver limit 2 A leaves margin -1 A, so the budget is fail.

2\ \text{A}\ -\ 3\ \text{A}=-1\ \text{A}

Three-ampere driver limit is exactly enough

6 bases at 1/2 A each total 3 A. Driver limit 3 A leaves margin 0 A, so the budget is pass.

3\ \text{A}\ -\ 3\ \text{A}=0\ \text{A}

Four-ampere driver limit leaves one ampere margin

6 bases at 1/2 A each total 3 A. Driver limit 4 A leaves margin 1 A, so the budget is pass.

4\ \text{A}\ -\ 3\ \text{A}=1\ \text{A}