Where does pinch-off collide?

In a field-effect transistor, pinch-off is the condition in which the conducting channel narrows to vanishing near the drain because the gate-to-channel voltage there falls below threshold, after which the drain current stops rising with drain voltage and the device enters saturation. Shockley's 1952 A unipolar “field-effect” transistor introduced the mechanism, and Sze and Ng's Physics of semiconductor devices gives the standard account of the pinch-off voltage and the saturated current. The referent is the voltage condition that saturates a FET, defined by the pinch-off (or threshold) voltage, a distinct construct from a liquid thread snapping in two, sharing only the image of a cross-section pinched shut.[1][2]

Unit

The pinch-off voltage at which the channel saturates the drain current

Recovery means

Not applicable

Measured by

Read from output I–V characteristics as the onset of current saturation, giving the pinch-off (threshold) voltage

In fluid dynamics, pinch-off is the moment a liquid thread or drop necks down to zero radius and separates, a finite-time singularity where surface tension drives the neck to collapse in a self-similar way independent of the initial conditions. Eggers's 1997 Nonlinear dynamics and breakup of free-surface flows is the authoritative account of this singular breakup and its universal scaling. The referent is the capillary breakup of a fluid interface, characterised by the self-similar thinning of the neck radius toward the singular instant, a different construct from a transistor channel closing, joined only by the shared word.[3]

Unit

The neck radius as it thins to zero at the breakup singularity

Recovery means

Not applicable

Measured by

Captured by high-speed imaging of the thinning neck and fitted to the self-similar scaling of radius versus time to breakup