The Metal Oxide
Semiconductor Field Effect Transistor MOS-FET was invented in
the late 50ies, say 10 years after the Bipolar Junction
Transistor (BJT)
You may look at a
BJT as a: Current generator controlled by a current
- meaning the current which lead into the base will result in a
larger collector current. Ic = hFE * Ib
The MOS-FET or
just MOS is controlled by an electric field - the base or gate
acts as one plate of a capacitor and when charged (positive or
negative depending on the MOS type) will the MOS be able to lead
a current.
You may look as MOS as a: Current generator controlled by
a voltage - or as a - Resistance controlled by a
voltage - which the case depends of the voltage ranges
(gate-source and drain-source).
CMOS - means
Complementary Metal Oxide Semiconductor and formed by a p-type
and a n-type MOS transistor. The CMOS inverter will only use
energy when the input changes state. xx% of the energy by
at shift goes to charge/ un-charge the capacitor (formed by the
gate) - the rest the energy lost at the stage where where the
gates got a voltage between
Vcc
and Gnd.
At this stage will both MOS -transistors have a resistance in
the range of say 1 kOhm, which could be regarded as a
Short-circuit
condition.
The most critical
situation will occur if the gates are
floating
- hence will you find build protection inside FPGA in form of
Pull-up / Pull-down or keeper devices in the IOB.
