Triac: A thyristor that can conduct in both directions. Because of this, it is useful for controlling alternating current. It is equivalent to two SCRs…

Transfer Function: The inputs and outputs of an op-amp circuit may be voltages, currents, or a combination of the two. When you use complex numbers…

Transconductance: The ratio of ac output current to ac input voltage. A measure of how effectively the input voltage controls the output current.

Threshold Voltage: The voltage that turns on an enhancement-mode MOSFET. At this voltage, an inversion layer connects the source to the drain.

Third Approximation: An accurate approximation of a diode or transistor. Used for designs that need to take into account as many details as possible.

Thevenin's theorem: A fundamental theorem that says any circuit driving a load can be converted to a single generator and series resistance.

Thermistor: A device whose resistance experiences large changes with temperature.

Thermal Shutdown: A feature found in modern three-terminal IC regulators. When the regulator exceeds a safe operating temperature, the pass transistor is cut off and…

Thermal Runaway: As a transistor heats, its junction temperature increases. This increases the collector current, which forces the junction temperature to increase further, producing more…

Temperature Coefficient: The rate of change of a quantity with respect to the temperature.

Switching Regulator: A linear regulator uses a transistor that operates in the linear region. A switching regulator uses a transistor that switches between saturation and…

Swamped Amplifier: A CE stage with a feedback resistor in the emitter circuit. This feedback resistor is much larger than the ac resistance of the…

Surge Current: The large initial current that flows through the diodes of a rectifier. It is the direct result of charging the filter capacitor, which…

Surface-Leakage Current: A reverse current that flows along the surface of a diode. It increases when you increase the reverse voltage.

Superposition: When you have several sources, you can determine the effect produced by each source acting alone and then add the individual effects, to get…