Input Offset Current: The difference of the two input currents to a diff amp or an op amp.

Input Bias Current: The average of the two input currents to a diff amp or an op amp.

Initial Slope of Sine Wave: The earliest part of a sine wave is a straight line. Tice slope of this line is the initial slope of the sine wave. This slope depends on the frequency and peak value of the sine wave.

Ideal transistor: The first approximation of a transistor. It assumes a transistor has only two parts: an emitter diode and a collector diode. The emitter diode is treated as an ideal diode, while the collector diode is a controlled current source. The current through the emitter diode controls the collector current source.

Ideal diode: The first approximation of a diode. The viewpoint is to visualize the diode as an intelligent switch that closes when forward-biased and opens when reverse-biased.

Ideal approximation: The simplest equivalent circuit of a device. It includes only a few basic features of the device and ignores many others of less importance.

Hysteresis: The difference between the two trip points of a Schmitt trigger. When used elsewhere, hysteresis refers to the difference between the two trip points on the transfer characteristic.

Hole: A vacancy in the valence orbit. For instance, each atom of a silicon crystal normally has eight electrons in the valence orbit. Heat energy may dislodge one of the valence electrons, producing a hole.

Holding Current: The minimum current through a thyristor that can keep it latched in the conducting stage.

High-frequency border: The frequency above which a capacitor acts as an ac short. Also, the frequency where the reactance is one-tenth of the total series resistance.

Heat Sink: A mass of metal attached to the case of a transistor to allow the heat to escape more easily.

Hartley oscillator: A circuit distinguished by its inductively tapped tank circuit.

Harmonics: A sine wave whose frequency is some integer multiple of a fundamental sine wave.

Hard Saturation: Operating a transistor at the upper end of the load line with a base current that is one-tenth of the collector current. The reason for the overkill is to make sure the transistor remains saturated under all operating conditions, temperature conditions, transistor replacement, etc.

Half-wave rectifier: A rectifier with only one diode in series with the load resistor. The output is a half-wave rectified voltage.