A front-end chain is only closed when the held input, gain stage, threshold decision, source drop, load voltage, and load current all agree. The checked path sends 2 V through gain 3 to 6 V, then leaves 8 V on the load at 2 A exactly for the ideal chain model; real front ends add offset, gain error, finite bandwidth, slew limits, rail headroom, source impedance, loading, noise, drift, and voltage/current measurement uncertainty.
A full front-end chain carries one exact voltage through hold, gain, threshold, and load. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The held node is amplified before the decision
The held input of 2 volts with gain 3 gives 6 volts.
Vgain=3⋅2V=6V
The HIGH rail drives a source and load
The output stage has a 4 volt source drop, leaving 8 volts across the load at 2 amperes.