Practical Electronics/Glossary

A

• Astable. An astable is a device that has no stable state, and oscillates continuously between the on and off states. An example is the 555 Timer IC in astable mode.

B

• Bistable. A bistable has two stable output state - on and off. Either state can remain indefinitely until reset or changed. An example is a flip-flop.

C

• Capacitance. This is the amount of charge that a capacitor or other device stores per volt of charging potential. It is measured in farads (F).

• Capacitor. A capacitor is a component that stores electric charge.

• Cycle. One complete repetition of a periodic signal.

D

• Diodes. A diode is a semiconductor device that allows charge to flow in one direction only.

E

F

• Farad. This is the unit of capacitance. One farad means that for every volt of chargin potential, one coulomb of charge is stored on the capacitor's plates.

• Frequency. The frequency of a signal is the number of times it repeats per second. It is measured in hertz (Hz).

G

• Graticule. The grid overlay on the screen of an oscilloscope.

H

• Hertz. The unit of frequency. One hertz means one cycle per second.

I

• Impedance.

J

• Joule. The joule is the unit of energy. It is equal to the energy require to lift a weight of one newton one metre in a gravitational field of ten metres per second per second (m s^-2)

M

• Monostable. A monostable is a device that has a stable state, and if disturbed from this state, it will revert back to the stable state after a given time.

• Multivibrator. Any of a class of digital circutis used to implement a variety of two-state systems like monostables, astables, flip-flops, etc.

O

• One-shot. A one-shot multivibrator is another name for a monostable.

P

• • Pull-up/Pull-down Resistors. These are resistors connected between a power rail and a logic input to ensure a valid input voltage is present under all conditions.

Q

• Quiescent current. This is current that flows though a device when there is no load present and which contributes nothing to the circuit's function. It is usually on the order of microamperes or milliamperes. It is also called leakage current. CMOS ICs have particularly low quiescent currents.

T

• Thermistor. A resitor which chances in resistance depending on its temperature.

• Thyristor. A transisitor that latches on once activated.

• Transient. A transient is a very short voltage change introduced into a circuit through poor voltage regulation or as a side effect of certain other techniques.

• Transistor. An electronic switch that is widely used in most aspects of electronics.

V

• Volt. The unit of potential difference. A potential difference of one volt means that each coulomb of charge has one joule of energy.

• Voltage. Another, less exact but more common, term for potential difference.

W

• Watt. The unit of power. One watt means that one joule of energy is used per second.