Control Threshold - Electronic Circuits II & III: Decision Networks and Interfaces Step by Step

A control-threshold scan derives the switch state from exact control and threshold voltages before computing current, so a control below threshold leaves I = 0 and a control above threshold closes the load path at I = V / R row by row. The arithmetic is exact only for the stated control voltages, threshold voltages, source voltages, load resistances, currents, switch states, and rows in the ideal controlled-switch model. Real transistor switches add saturation voltage, leakage, gain spread, resistor tolerance, input threshold variation, probe/calibration limits, finite precision, and measurement uncertainty.

The helper derives switch state from exact control and threshold voltages before it computes current. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Below threshold leaves no load current

The lower control is 2 volts, below the threshold, so the load current is 0 amperes.

2\ \text{V} < 3\ \text{V}

Above threshold closes the load path

The higher control is 5 volts, above the same threshold, so the load current becomes 3 amperes.

5\ \text{V} > 3\ \text{V}\Rightarrow I = 3\ \text{A}