Unijunction Transistor (UJT): This low-power thyristor is useful in electronic timing, waveshaping, and control applications.

Ultra-Large-Scale Integration (ULSI): The placing of more than 1 million components on a single chip.

Two-Supply Emitter Bias (TSEB): A power supply that produces both positive and negative supply voltages.

Two-State Output: This is the output voltage from a digital or switching circuit. It is referred to as two-state because the output has only two stable states: low and high. The region between the low and high voltages is unstable because the circuit cannot have any value in this range except temporarily when switching between states.

Twin-T oscillator: An oscillator that receives the positive feedback to the noninverting input through a voltage divider and the negative feedback through the twin-T filter.

Trip Point: The value of the input voltage that switches the output of a comparator or Schmitt trigger.

Trigger Voltage: The minimum voltage needed to turn on a thyristor.

Trigger Current: The minimum current needed to turn on a thyristor.

Trigger: A sharp pulse of voltage and current that is used to turn on a thyristor or other switching device.

Trial and Error: Suppose you have a problem involving two simultaneous equations. Instead of solving this in the usual left-brain mathematical way, you can guess an answer and then calculate all the unknowns. One of the calculated unknowns is the very answer that you guessed. You compare the calculated and guessed answers to see how different they are. Then you guess another answer that will close the gap between the guessed and calculated answers. After several trials, the gap becomes small enough that you have an approximate answer.

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 in parallel with opposite polarities.

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 for the input and output quantities, the ratio of output to input becomes a function of the frequency. The name for the ratio is the transfer function.

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.