A: Abbreviation for ampere, the unit of electrical current.
AC Coupling: Circuit that passes an AC signal while blocking a DC voltage.
ADC: Abbreviation for Analog to Digital Converter.
Alpha: Ratio of collector current to emitter current in a bipolar junction transistor (BJT). Greek letter alpha “α” is the symbol used.
Amplifier: A circuit that increases the voltage, current, or power of a signal.
Amplitude: Magnitude or size of a signal voltage or current.
Analog: Information represented as continuously varying voltage or current rather than in discrete levels as opposed to digital data varying between two discrete levels.
Anode: The positive electrode or terminal of a device. The “P” material of a diode.
Astable: A circuit that cannot remain in one state. That is it will periodically switch between states or oscillate.
Attenuate: To reduce the amplitude of an action or signal. The opposite of amplification.
Average value: A value of voltage or current where the area of the wave above the value equals the area of the wave below the value.
AWG: Abbreviation for Arbitrary Waveform Generator or American Wire Gauge.
Bandwidth: Width of the band of frequencies between the half power points.
Barrier potential: The natural difference of potential that exists across a forward-biased PN junction.
Base: The region that lies between the emitter and collector of a bipolar junction transistor (BJT).
Beta (β): The ratio of collector current to base current in a bipolar junction transistor (BJT).
Bias: A DC voltage applied to a device to control its operation.
Bipolar junction transistor (BJT): A three-terminal device in which emitter to collector current is controlled by base current.
Bode plot: A graph of gain versus frequency.
Branch current: The portion of the total current flowing in one path of a parallel circuit.
Breakdown voltage: Voltage at which the breakdown of a dielectric or insulator occurs.
Bridge rectifier: A circuit using four diodes to provide full wave rectification. Converts an AC voltage to a pulsating DC voltage.
Buffer: An amplifier used to isolate a load from a source.
BW: Abbreviation for bandwidth.
Bypass capacitor: A capacitor used to provide an AC ground at some point in a circuit.
Calibration: To adjust the correct value of a reading by comparison to a standard.
Capacitance: The ability of a capacitor to store an electrical charge. The basic unit of capacitance is the Farad.
Capacitor: An electronic component having capacitive reactance.
Cascaded amplifier: An amplifier with two or more stages arranged in a series configuration.
Cascode amplifier: A high frequency amplifier made up of a common-source or common-emitter amplifier with a common-gate or common base amplifier in its drain/collector network.
Cathode: The negative terminal electrode of a device. The “N” material in a junction diode.
Center-tapped rectifier: Circuit that make use of a center tapped transformer and two diodes to provide full wave rectification.
Center-tapped transformer: A transformer with a connection at the electrical center of a winding.
Charge: Quantity of electrical energy.
Circuit: Interconnection of components to provide an electrical path between two or more components.
Clamp: A diode circuit used to change the DC level of a waveform without distorting the waveform.
Class A amplifier: A linear amplifier biased so the active device conducts through 360 degrees of the input waveform.
Class B amplifier: An amplifier with two active devices. The active components are biased so that each conducts for approximately 180 degrees of the input waveform cycle.
Class C amplifier: An amplifier in which the active device conducts for less than 180 degrees of the input waveform cycle.
Clipper: A diode circuit used to eliminate part of a waveform above or below a limit.
Closed circuit: Circuit having a complete path for current flow.
Closed-loop gain: Gain of an amplifier when a feedback path is present.
Collector: The semiconductor region in a bipolar junction transistor through which a flow of charge carriers leaves the base region.
Collector characteristic curve: A graph of collector voltage over collector current for a given base current.
Common base amplifier: A BJT circuit in which the base connection is common to both input and output.
Common collector amplifier: A BJT circuit in which the collector connection is common to both input and output.
Common drain amplifier: A FET circuit in which the drain connection is common to both input and output.
Common emitter amplifier: A BJT circuit in which the emitter connection is common to both input and output.
Common gate amplifier: A FET circuit in which the gate connection is common to both input and output.
Common source amplifier: A FET circuit in which the source connection is common to both input and output.
Common-mode rejection ratio (CMRR): The ratio of op-amp differential gain to common-mode gain. A measure of an op-amp’s ability to reject common-mode signals such as noise.
Common-mode signals: Signals that appear simultaneously at two inputs of an operational amplifier (op-amp). Common mode signals are always equal in amplitude and phase.
CMOS: Complimentary MOSFET logic. CMOS logic dominates the digital industry because the power requirements and component density are significantly better than other technologies.
Comparator: An op-amp circuit that compares two inputs and provides a DC output indicating the polarity relationship between the inputs.
Complementary transistors: Two transistors, one NPN and one PNP having near identical characteristics. N-channel and P-channel FETs can also be complementary.
Constant current circuit: Circuit used to maintain constant current to a load having resistance that changes.
Conventional current flow: Concept of current produced by the movement of positive charges towards the negative terminal of a source.
Coulomb: Unit of electric charge. A negative coulomb charge consists of 6.24 × 1018 electrons.
Coupling: To electronically connect two circuits so that signal will pass from one to the other.
Current: Measured in amperes, it is the flow of electrons through a conductor. Also known as electron flow.
Current amplifier: Amplifier to increase signal current.
Current divider: Parallel network designed to divide the total current of a circuit.
Current feedback: Feedback configuration where a portion of the output current is fed back to the amplifier input.
Current mirror: Term used to describe the fact that DC current through the base circuit of a class B amplifier is approximately equal to the DC collector current.
Cutoff: Condition when an active device is biased such that output current is near zero or beyond zero.
DAC: Abbreviation for “digital to analog converter.”
Darlington pair: An amplifier consisting of two bipolar junction transistors with their collectors connected together and the emitter of one connected to the base of the other. This circuit has an extremely high current gain and input impedance.
DC: Abbreviation for “direct current”.
DC load line: A graph representing all possible combinations of voltage and current for a given load resistor in an amplifier.
DC offset: The change in input voltage required to produce a zero output voltage when no signal is applied to an amplifier.
DC power supply: Any source of DC power for electrical equipment.
Decade: A frequency factor of ten.
Decibel (dB): A logarithmic representation of gain or loss.
Degenerative feedback: Also called negative feedback. A portion of the output of an amplifier is inverted and connected back to the input. This controls the gain of the amplifier and reduces distortion and noise.
Depletion layer or region: The area surrounding a PN junction that is depleted of carriers.
Depletion mode: In a FET, an operating mode where reverse gate-source voltage is used to deplete the channel of free carriers. This reduces the size of the channel and increases its resistance.
Depletion-mode MOSFET: A MOSFET designed to operate in either depletion mode or enhancement mode.
Device: A component or part.
Dielectric: Insulating material between two plates where an electrostatic field exists.
Dielectric constant: Property of a material that determines how much electrostatic energy can be stored per unit volume when unit voltage is applied.
Dielectric strength: The maximum voltage an insulating material can withstand without breaking down.
Differential amplifier: An amplifier in which the output is in proportion to the differences between voltages applied to its two inputs.
Differentiator: A circuit in which the output voltage is in proportion to the rate of change of the input voltage.
Diffusion: Tendency of conduction band electrons to wander across a PN junction to combine with valence band holes.
Digital: Relating to devices or circuits that have outputs of only two discrete levels. Examples: 0 or 1, high or low, on or off, true or false etc.
Diode: A two-terminal device that conducts in only one direction.
Direct coupling: Where the output of one amplifier stage is connected directly to the input of a second amplifier or to a load. Also known as DC coupling because DC signals are not blocked.
Direct current (DC): Current that flows, on average, in only one direction.
Doping: The process of adding impurity atoms to intrinsic (pure) silicon or germanium to improve the conductivity of the semiconductor material.
Duty cycle: The duty cycle is the fraction of one period in which a signal or system is active. Duty cycle is commonly expressed as a percentage or a ratio. A period is the time it takes for a signal to complete an on-and-off cycle.
Electric charge: Electric energy stored on the surface of a material. Also known as a static charge.
Electric field: A field or force that exists in the space between two different potentials or voltages. Also known as an electrostatic field.
Electromotive force (emf): Force that causes the motion of electrons due to potential difference between two points (voltage).
Electron: Smallest sub atomic particle of negative charge that orbits the nucleus of an atom.
Electron flow: Electrical current produced by the movement of free electrons towards a positive terminal.
Electrostatic: Related to static electric charge.
Emitter: The semiconductor region from which charge carriers are injected into the base of a bipolar junction transistor.
Emitter feedback: Coupling from the emitter output to the base input of a bipolar junction transistor.
Emitter follower: A common collector amplifier. Has a high current gain, high input impedance and low output impedance.
Engineering notation: A floating point system in which numbers are expressed as products consisting of a number greater than one multiplied by an appropriate power of ten that is some multiple of three.
Enhancement-mode MOSFET: A field effect transistor in which there are no charge carriers in the channel when the gate source voltage is zero.
Equivalent resistance: Total resistance of all the individual resistances in a circuit.
Fall time: Time it takes the falling edge of a pulse to go from 90% of peak voltage to 10% of peak voltage.
Farad: The basic unit of capacitance.
Feedback: A portion of the output signal of an amplifier which is connected back to the input of the same amplifier.
Feedback amplifier: An amplifier with an external signal path from its output back to its input.
Field effect transistor (FET): A voltage controlled transistor in which the source to drain conduction is controlled by gate to source voltage.
Filter (passive): Network consisting of capacitors, resistors and/or inductors used to pass certain frequencies and block others.
Flip Flop: A digital circuit that flips or toggles between two stable states (bistable). The Flip Flop inputs decide which of the two states its output will be.
Forward bias: A PN junction bias which allows current to flow through the junction. Forward bias decreases the resistance of the depletion layer.
Free electrons: Electrons that are not in any orbit around a nucleus.
Frequency-domain analysis: A method of representing a waveform by plotting its amplitude against frequency.
Frequency response: Indication of how well a circuit responds to different frequencies applied to it.
Frequency response curve: A graph of amplitude over frequency indicating a circuit response to different frequencies.
Full wave rectifier: Rectifier that makes use of the full AC wave in both the positive and negative half cycles.
Function generator: Signal generator that can produce sine, square, triangle and sawtooth output waveforms.
Fundamental frequency: Lowest frequency in a complex waveform.
Gain: Increase in voltage, current and/or power. Gain is expressed as a ratio of amplifier output value to the corresponding amplifier input value.
Gain bandwidth product: A device parameter that indicates the maximum possible product of gain and bandwidth. The gain bandwidth product of a device is equal to the unity gain frequency of the device.
GPIB: General-purpose instrument bus, also known as the IEEE-488 bus, widely used as an interface for connecting test instruments to computers and for providing programmable instrument control.
Ground: An intentional or accidental conducting path between an electrical system or circuit and the earth or some conducting body acting in place of the earth. A ground is often used as the common wiring point or reference in a circuit.
Half power point: A frequency at which the power is 50% of maximum. This corresponds to 70.7% of maximum current or voltage.
H-parameters (hybrid parameters): Transistor specifications that describe the component operating limits under specific circumstances.
Half wave rectifier: A diode rectifier that converts AC to pulsating DC by eliminating either the negative or the positive alternation of each input AC cycle.
Harmonic: Sine wave that is smaller in amplitude and some multiple of a fundamental frequency. Example: 880 Hz. is the second harmonic of 440 Hz., 880 Hz. is the third harmonic of 220 Hz.
Harmonics: A frequency component of a signal that is an integral multiple of the fundamental of that signal.
Hole: A gap left in the covalent bond when a valence electron gains sufficient energy to jump to the conduction band.
I2C: Inter integrated circuit bus, a short-distance serial communication bus standard consisting of two signals (clock and data), popular for talking between several integrated circuits on the same printed circuit board.
IC: Abbreviation for “integrated circuit”.
IC voltage regulator: Three terminal device used to hold the output voltage of a power supply constant over a wide range of load variations.
Impedance (Z): Measured in ohms it is the total opposition to the flow of current offered by a circuit. Impedance consists of the vector sum of resistance and reactance.
Interleave: A technique used in digitizing oscilloscopes whereby ADCs of different analog channels are used together, normally resulting in higher sample rate or more memory depth when you are using fewer channels.
Internal resistance: Every source has some resistance in series with the output current. When current is drawn from the source some power is lost due to the voltage drop across the internal resistance. Usually called output impedance or output resistance.
Intrinsic material: A semiconductor material with electrical properties essentially characteristic of ideal pure crystal. Essentially silicon or germanium crystal with no measurable impurities.
Inverting amplifier: An amplifier that has a 180° phase shift from input to output.
Inverting input: In an operational amplifier (op amp) the input that is marked with a minus sign. A signal applied at the inverting input will be given 180° phase shift between input and output.
Ion: An atom with fewer electrons in orbit than the number of protons in the nucleus is a positive ion. An atom with a greater number of electrons in orbit than the number of protons in the nucleus is a negative ion.
Junction: Contact or connection between two or more wires or cables. The area where the p-type material and n-type material meet in a semiconductor.
Junction diode: A semiconductor diode in which the rectifying characteristics occur at a junction between the n-type and p-type semiconductor materials.
Kilo: Metric prefix for 1000.
Kirchhoff’s current law: The sum of the currents flowing into a point in a circuit is equal to the sum of the currents flowing out of that same point.
Kirchhoff’s voltage law: The algebraic sum of the voltage drops in a closed path circuit is equal to the algebraic sum of the source voltages applied.
Knee voltage: The voltage at which a curve joins two relatively straight portions of a characteristic curve. For a PN junction diode, the point in the forward operating region of the characteristic curve where conduction starts to increase rapidly. For a zener diode, the term is often used in reference to the zener voltage rating.
L-C tank circuit: A circuit consisting of inductance and capacitance, capable of storing electricity over a band of frequencies continuously distributed about a single frequency at which the circuit is said to be resonant or tuned.
Light-emitting diode (LED): A semiconductor diode that converts electric energy into electromagnetic radiation at a visible and near infrared frequencies when its pn junction is forward biased.
Limiter: Circuit or device that prevents some portion of its input from reaching the output.
Linear: Relationship between input and output in which the output varies in direct proportion to the input.
Linear scale: A scale in which the divisions are uniformly spaced.
Line regulation: The ability of a voltage regulator to maintain a constant voltage when the regulator input voltage varies.
Load: A source drives a load. Whatever component or piece of equipment is connected to a source and draws current from a source is a load on that source.
Load current: Current drawn from a source by a load.
Load impedance: Vector sum of reactance and resistance in a load.
Load regulation: The ability of a voltage regulator to maintain a constant output voltage under varying load currents. load resistance Resistance of a load.
Majority carriers: The conduction band electrons in an n-type material and the valence band holes in a p-type material. Produced by pentavalent impurities in n-type material and trivalent impurities in p-type material.
Metal oxide field effect transistor (MOSFET): A field effect transistor in which the insulating layer between the gate electrode and the channel is a metal oxide layer.
Mid-band gain: Gain of an amplifier operating within its bandwidth.
Mid-point bias: An amplifier biased at the center of its DC load line.
mil: One thousandth of an inch (0.001 in.).
Miller’s theorem: A theorem that allows you to represent a feedback capacitor as equivalent input and output shunt capacitors.
Minority carriers: The conduction band holes in n-type material and valence band electrons in p-type material. Most minority carriers are produced by temperature rather than by doping with impurities.
Monostable: A circuit that has one stable state. When perturbed, the circuit will return to the stable state after some fixed amount of time.
MOSFET: Abbreviation for “metal oxide field effect transistor” also known as an “insulated gate field effect transistor. A field effect transistor in which the insulating layer between the gate electrode and the channel is a metal oxide layer.
Multivibrator: A circuit used to implement a simple two-state system, which may be astable, monostable, or bistable.
N-type semiconductor: A semiconductor compound formed by doping an intrinsic semiconductor with a pentavalent element. An n-type material contains an excess of conduction band electrons.
Negative: Terminal that has an excess of electrons.
Negative charge: A charge that has more electrons than protons.
Negative feedback: A feedback signal 180° out of phase with an amplifier input signal. Used to increase amplifier stability, bandwidth and input impedance. Also reduces distortion.
Negative ion: An atom having a greater number of electrons in orbit than there are protons in the nucleus.
Negative resistance: A resistance such that when the current through it increases the voltage drop across the resistance decreases.
Negative temperature coefficient: A term used to describe a component whose resistance or capacitance decreases when temperature increases.
Node: Junction or branch point in a circuit.
Noise: Unwanted electromagnetic radiation within an electrical or mechanical system.
Non-inverting input: The terminal on an operational amplifier that is identified by a plus sign.
Non-linear scale: A scale in which the divisions are not equally spaced, logarithmic.
Norton’s theorem: Any network of voltage sources and resistors can be replaced by a single current source in parallel with a single resistor.
NPN transistor: A bipolar junction transistor in which a p-type base element is sandwiched between an n-type emitter and an n-type collector.
One Shot: Monostable circuit that produces one pulse when triggered.
Open-loop gain: The open-loop gain of an operational amplifier is the gain obtained when no feedback is used in the circuit. Open-loop gain is usually exceedingly high; in fact, an ideal operational amplifier has infinite open-loop gain. Typically an op-amp may have an open-loop gain of around 100,000. Normally, feedback is applied around the op-amp so that the gain of the overall circuit is defined and kept to a figure which is more usable. However the very high gain of the op-amp enables considerable levels of feedback to be applied to achieve required performance. The open-loop gain of an operational amplifier falls very rapidly with increasing frequency. Along with slew rate, this is one of the reasons why operational amplifiers have limited bandwidth.
Passive component: Component that does not amplify a signal. Resistors, capacitors and inductors are examples.
Peak to peak: Difference between the maximum positive and maximum negative values of an AC waveform.
Percent of regulation: The change in output voltage that occurs between no-load and full-load in a DC voltage source. Dividing this change by the full-load value and multiplying the result by 100 gives percent regulation.
Percent of ripple: The ratio of the effective rms value of ripple voltage to the average value of the total voltage. Expressed as a percentage.
Pinch-off region: A region on the characteristic curve of a FET in which the gate bias causes the depletion region to extend completely across the channel.
PNP transistor: A bipolar junction transistor with an n-type base and p-type emitter and collector.
Positive feedback: A feedback signal that is in phase with an amplifier input signal. Positive feedback is necessary for oscillation to occur.
Potential difference: Voltage difference between two points which will cause current to flow in a closed circuit.
Potentiometer: A variable resistor with three terminals. Mechanical turning of a shaft can be used to produce variable resistance and potential. Example: A volume control is usually a potentiometer.
Power supply rejection ratio (PSRR): A measure of an op-amps ability to maintain a constant output when the supply voltage varies.
Protoboard: Board with provision for attaching components without solder. Also called a breadboard. Primarily used for constructing experimental circuits.
RC time constant: Product of resistance and capacitance in seconds.
Recombination: Process by which a conduction band electron gives up energy (in the form of heat or light) and falls into a valence band hole.
Rectification: Process that converts alternating current to direct current.
Rectifier: Diode circuit that converts alternating current into pulsating direct current.
Regenerative feedback: Positive feedback. Feedback from the output of an amplifier to the input such that the feedback signal is in phase with the input signal. Used to produce oscillation.
Regulated power supply: Power supply that maintains a constant output voltage under changing load conditions.
Regulator: Device or circuit that maintains a desired output under changing conditions.
Resistance: Symbolized “R” and measured in ohms. Opposition to current flow and dissipation of energy in the form of heat.
Resistor: Component made of material that opposes flow of current and therefore has some value of resistance.
Reverse bias: Bias on a PN junction that allows only leakage current (minority carriers) to flow. Positive polarity on the n-type material and negative polarity to the p-type material.
Reverse breakdown voltage: Amount of reverse bias that will cause a PN junction to break down and conduct in the reverse direction.
Reverse current: Current through a diode when reverse biased. An extremely small current also referred to as leakage.
Reverse saturation current: Reverse current through a diode caused by thermal activity. This current is not affected by the amount of reverse bias on the component but does vary with temperature.
Saturation: Condition in which a further increase in one variable produces no further increase in the resultant effect. In a bipolar junction transistor, the condition when the emitter to collector voltage is less than the emitter to base voltage.
Schematic diagram: Illustration of an electrical or electronic circuit with the components represented by their symbols.
Scientific notation: Numbers entered as a number from one to ten multiplied by a power of ten.
Self biasing: Gate bias for a field effect transistor in which source current through a resistor produces the voltage for gate to source bias.
Semiconductor: An element which is neither a good conductor or a good insulator, but rather lies somewhere between the two. Characterized by a valence shell containing four electrons. Silicon, germanium and carbon are the semiconductors most frequently used in electronics.
Series circuit: Circuit in which the components are connected end to end so that current has only one path to follow through the circuit.
Signal to noise ratio (SNR): Ratio of the magnitude of the signal to the magnitude of noise usually expressed in decibels.
Silicon (Si): Non metallic element (atomic number 14) used in pure form as a semiconductor.
Silicon dioxide: Glass like material used as the gate insulating material in a MOSFET.
Silicon transistor: A bipolar junction transistor using silicon as the semi conducting material.
Solid state: Pertaining to circuits where signals pass through solid semiconductor material such as transistors and diodes as opposed to vacuum tubes where signals pass through a vacuum.
Source follower: FET amplifier in which signal is applied between gate and drain with output taken between source and drain. Also called “common drain”.
Source impedance: Impedance through which output current is taken from a source.
Spectrum analyzer: Instrument used to display the frequency domain of a waveform plotting amplitude against frequency.
SPI: Serial Peripheral Interface, a very simple short-distance serial communication bus standard consisting of either two (clock and data) or three (clock, data and strobe) signals, popular for reading data from microcontroller peripherals such as ADCs.
Summing amplifier: An op-amp circuit whose output is proportional to the sum of its instantaneous voltages.
Superposition theorem: Theorem designed to simplify networks containing two or more sources. It states that in a network containing more than one source, the current at any one point is equal to the algebraic sum of the currents produced by each source acting separately.
Thévenin’s theorem: Theorem that replaces any complex network with a single voltage source in series with a single resistance.
Threshold voltage: For an enhancement MOSFET, the minimum gate-source voltage required for conduction of source drain current.
Transconductance: Also called mutual conductance. Ratio of a change in output current to the change in input voltage that caused it.
Transistor: Term derived from “transfer resistor”. Semiconductor device that can be used as an amplifier or as an electronic switch.
Trivalent element: One having three valence electrons. Used as an impurity in semiconductor material to produce p-type material. Most commonly used trivalent elements are: Aluminum, Gallium and Boron.
Unity gain frequency: Frequency of operation for a device where the gain of the component drops to unity.
USB: Universal Serial Bus, an interface for connecting peripherals, including test instruments, to computers.
Valence shell: The outermost electron shell for a given atom. The number of electrons in this shell determines the conductivity of the atom.
Varactor diode: PN junction diode with a high junction capacitance when reverse biased. Most often used as a voltage controlled capacitor.
Variable capacitor: Capacitor whose capacitance can be change by varying the effective area of the plates or the distance between the plates.
Variable resistor: Resistor whose resistance can be changed by turning a shaft. See also “potentiometer and rheostat”.
Virtual ground: Point in a circuit that is always at approximately ground potential. Often a ground for voltage, but not for current. The summing junction in an op-amp circuit.
Volt: Unit of potential difference or electromotive force. One volt is the potential difference needed to produce one ampere of current through a resistance of one ohm.
Voltage (V): Term used to designate electrical pressure or force that causes current to flow.
Voltage amplifier: Amplifier designed to build up signal voltage. By design, amplifiers can have a large voltage gain or a large current gain, or a large power gain. Voltage amplifiers are designed to maximize voltage gain often at the expense of current gain or power gain.
Voltage divider: Fixed or variable series resistor network connected across a voltage to obtain a desired fraction of that voltage.
Voltage divider biasing: Biasing method used with amplifiers in which two series resistors connected across a source. The junction of the two biasing resistors provides correct bias voltage for the amplifier.
Voltage drop: Voltage or difference in potential developed across a component due to current flow.
Voltage feedback: Feedback configuration where a portion of the output voltage is fed back to the input of an amplifier.
Voltage follower: Operational amplifier circuit characterized by a high input impedance, low output impedance and unity voltage gain. Used as a buffer between a source and a low impedance load.
Voltage gain: Also called voltage amplification. Ratio of amplifier output voltage to input voltage usually expressed in decibels.
Voltage multiplier: Rectifier circuit using diodes and capacitors to produce a DC output voltage that is some multiple of the peak value of AC input voltage. Cost effective way of producing higher DC voltages. Voltage doublers and voltage triplers are examples.
Voltage regulator: Device or circuit that maintains constant output voltage (within certain limits) in spite of changing line voltage and/or load current.
Voltage source: Circuit or device that supplies voltage to a load.
Zener diode: Semiconductor diode in which reverse breakdown voltage current causes the diode to develop a constant voltage. Used as a clamp for voltage regulation.