SubThreshold.com
A central location for SubThreshold design information.

Member of: Equations

SubThreshold Conditions

Technically, subthreshold can be defined as (Q_S is the channel charge), but this definition is not much help practically. Instead subthreshold conditions are best defined by the biasing current range. The correct biasing currents those over which I_D is exponentially related to V_GS. For instance, in a 0.5μ process an I_D in the 100fA - 100 nA usually places a transistor in the subthreshold region.

To find I_D for your process, plot V_GS vs. log(I_D) and identify the voltage and current range over which the curve is linear. Remember also the transistor dimensions play a part in this too.

See Also:

• Regions Of Operation

Back Links: