Glossary

Glossary #

A comprehensive reference of electronics and SPICE simulation terminology used in Breadpad.

A #

AC Analysis
Frequency-domain analysis that shows how a circuit responds to different frequencies. Used for filter design, amplifier bandwidth analysis, and stability testing.
Active Component
Components that can amplify signals or control current flow (transistors, operational amplifiers, etc.).
Anode
The positive terminal of a diode or LED. Current flows from anode to cathode.
Astable
An oscillator circuit with no stable state, continuously switching between two states (e.g., 555 timer in astable mode).

B #

Bandwidth
The frequency range over which a circuit operates effectively, typically measured between -3dB points.
Beta (β)
The current gain of a bipolar junction transistor, defined as IC/IB.
Bias
The DC voltages and currents that establish the operating point of active components.
BJT (Bipolar Junction Transistor)
A three-terminal semiconductor device (collector, base, emitter) that amplifies current. Available in NPN and PNP types.
Breadboard
A prototyping platform with a grid of tie points for building temporary circuits without soldering.
Bulk Terminal
The fourth terminal of a MOSFET (substrate connection), often connected to source.

C #

Capacitance
The ability to store electric charge, measured in Farads (F). Common units: μF (microfarads), nF (nanofarads), pF (picofarads).
Cathode
The negative terminal of a diode or LED. Marked with a stripe or arrow in circuit symbols.
Common Mode
Signals that appear equally on both inputs of a differential amplifier.
Convergence
The process by which SPICE iteratively finds a solution to circuit equations. Convergence failure means no solution was found.
Cutoff Frequency
The frequency at which a filter’s output is reduced by -3dB (approximately 70.7% of maximum).

D #

DC Operating Point
The steady-state DC voltages and currents in a circuit when all AC signals are removed.
DC Sweep
Analysis that varies a voltage or current source and observes circuit behavior across that range.
Dead Zone
The minimum input required before a controller responds (relevant for gamepad settings).
Depletion Mode
FET type that conducts when gate voltage is zero and is turned off by applying gate voltage.
Dielectric
The insulating material between capacitor plates that determines capacitance value.
Differential Pair
Two matched transistors used to amplify the difference between two input signals.
Duty Cycle
In PWM signals, the percentage of time the signal is high during one period.

E #

Early Voltage (VA)
A BJT parameter modeling output resistance in the active region.
Emitter Degeneration
A resistor in the emitter circuit that improves stability and linearity at the cost of gain.
Enhancement Mode
FET type that is normally off and conducts when sufficient gate voltage is applied.
ESR (Equivalent Series Resistance)
The resistive component of a capacitor’s impedance, important at high frequencies.

F #

Farads (F)
Unit of capacitance. Common prefixes: μF (10⁻⁶), nF (10⁻⁹), pF (10⁻¹²).
Forward Voltage (Vf)
The voltage drop across a conducting diode, typically 0.7V for silicon, 2-3V for LEDs.
Frequency Response
How a circuit’s gain and phase shift vary with input frequency.

G #

Gain
The ratio of output signal to input signal. Can be voltage gain (Av), current gain (Ai), or power gain (Ap).
Gate
The control terminal of a field-effect transistor (FET or MOSFET).
Ground (GND)
The reference point for voltages in a circuit, assigned 0V by convention.
Gaussian Distribution
The statistical distribution used in Monte Carlo analysis for component tolerances.

H #

Harmonic
Frequency components at integer multiples of a fundamental frequency.
Henries (H)
Unit of inductance. Common prefixes: mH (millihenries), μH (microhenries).
High-Pass Filter
Circuit that allows high frequencies to pass while attenuating low frequencies.

I #

Impedance (Z)
The total opposition to AC current, combining resistance, capacitive reactance, and inductive reactance.
Inductance
The property of a conductor that opposes changes in current, measured in Henries (H).
Initial Condition (IC)
Starting voltages on capacitors or currents through inductors at t=0.
Input Impedance
The impedance seen by a signal source when connected to a circuit’s input.

J #

JFET (Junction Field-Effect Transistor)
A voltage-controlled device with gate, drain, and source terminals. Operates in depletion mode.
Junction Capacitance
The capacitance formed at the PN junction of diodes and transistors.

K #

Kirchhoff’s Current Law (KCL)
The sum of currents entering a node equals the sum of currents leaving.
Kirchhoff’s Voltage Law (KVL)
The sum of voltages around any closed loop in a circuit equals zero.

L #

Lambda (λ)
MOSFET parameter representing channel-length modulation (output conductance effect).
Linearization
The process of approximating a nonlinear circuit around an operating point for small-signal analysis.
Load Line
Graphical representation of possible operating points for an amplifier stage.
Low-Pass Filter
Circuit that allows low frequencies to pass while attenuating high frequencies.

M #

MFi (Made for iPhone/iPad)
Apple certification for accessories, including game controllers.
Monostable
A circuit with one stable state, producing a single pulse output when triggered.
Monte Carlo Analysis
Statistical simulation that randomly varies component values within tolerances to analyze circuit variations.
MOSFET (Metal-Oxide-Semiconductor FET)
A voltage-controlled transistor with very high input impedance. Types: NMOS, PMOS.

N #

Netlist
A text description of a circuit listing all components and their connections.
ngspice
The open-source SPICE simulation engine used by Breadpad.
Node
A connection point in a circuit where two or more components meet.
Noise
Unwanted random variations in voltage or current, measured in V/√Hz.
NPN
Bipolar transistor type where current flows from collector to emitter when base is positive.

O #

Ohm’s Law
Fundamental relationship: V = IR (Voltage = Current × Resistance).
Operating Point
See DC Operating Point.
Output Impedance
The impedance seen looking back into a circuit’s output terminals.

P #

Parasitic
Unintended circuit elements (resistance, capacitance, inductance) that affect high-frequency or precision performance.
Passive Component
Components that cannot amplify (resistors, capacitors, inductors).
PCB (Printed Circuit Board)
Permanent circuit board with copper traces connecting components.
Phase Shift
The time delay between input and output signals, expressed in degrees or radians.
PNP
Bipolar transistor type where current flows from emitter to collector when base is negative.
Pole
A frequency point where circuit gain decreases by 20dB/decade in frequency response.
Probe
Measurement point in Breadpad to monitor voltage or current during simulation.
Pull-up/Pull-down Resistor
Resistor that ensures a node defaults to high (pull-up) or low (pull-down) when not actively driven.
PWM (Pulse Width Modulation)
Signal encoding information in the duty cycle of a pulse train.

Q #

Q Factor (Quality Factor)
Measure of filter selectivity or oscillator stability. Higher Q = narrower bandwidth.
Quiescent Current
The DC current drawn by a circuit with no signal applied.

R #

Reactance
Opposition to AC current by capacitors (XC = 1/2πfC) or inductors (XL = 2πfL).
Reference Voltage
A stable, known voltage used for comparisons or biasing.
Resonance
Frequency at which inductive and capacitive reactances cancel, causing maximum response.
Reverse Bias
Applying voltage to a diode or transistor junction in the non-conducting direction.
RMS (Root Mean Square)
Effective value of an AC signal: the DC value that would deliver the same power.

S #

Saturation
BJT operating region where collector-emitter voltage is minimum and device acts like a closed switch.
Schematic
Diagram showing circuit connections using standard symbols.
SI Prefix
Standard metric prefixes (k=kilo, M=mega, m=milli, μ=micro, n=nano, p=pico).
Small-Signal Analysis
Analysis of circuit behavior for small variations around the DC operating point.
SPICE (Simulation Program with Integrated Circuit Emphasis)
Industry-standard circuit simulator.
Subcircuit (.SUBCKT)
Reusable circuit block defined once and instantiated multiple times.

T #

Temperature Coefficient (TC)
How component value changes with temperature, typically in ppm/°C.
Thevenin Equivalent
Any two-terminal linear circuit can be replaced by a voltage source and series resistance.
Threshold Voltage (VTO)
MOSFET gate voltage required to begin conduction.
Tie Point
Connection point on a breadboard; in Breadpad, the grid positions where components can be placed.
Time Constant (τ)
Time for exponential response to reach 63.2% of final value. τ = RC or τ = L/R.
Tolerance
Allowed variation in component value, expressed as percentage (e.g., ±5%).
Transconductance (gm)
The ratio of output current change to input voltage change in a transistor.
Transient Analysis
Time-domain simulation showing how voltages and currents change over time.
Transmission Line
Distributed circuit model for high-frequency signal propagation, with characteristic impedance.

U #

Unity Gain Frequency (fT)
Frequency at which transistor current gain drops to 1.

V #

VBE
Base-emitter voltage in a BJT, typically 0.7V when conducting.
VCE
Collector-emitter voltage in a BJT.
VDS
Drain-source voltage in a FET.
VGS
Gate-source voltage in a FET.
Voltage Divider
Two resistors in series that produce an output voltage proportional to their ratio.
Voltage Source
Component that maintains a specified voltage regardless of current (ideal) or within limits (real).

W #

Waveform
The shape of an electrical signal when plotted against time.

X #

XC (Capacitive Reactance)
Opposition to AC current by a capacitor: XC = 1/(2πfC).
XL (Inductive Reactance)
Opposition to AC current by an inductor: XL = 2πfL.

Z #

Zero
A frequency point where circuit gain increases by 20dB/decade in frequency response.
Z (Impedance)
See Impedance.

SPICE-Specific Terms #

.AC
SPICE command for AC small-signal analysis.
.DC
SPICE command for DC sweep analysis.
.MODEL
SPICE command defining component parameters.
.OP
SPICE command for operating point analysis.
.PARAM
SPICE command for defining parameters/variables.
.PRINT/.PLOT/.PROBE
SPICE commands for output control.
.SUBCKT/.ENDS
SPICE commands for defining subcircuits.
.TEMP
SPICE command for setting simulation temperature.
.TRAN
SPICE command for transient analysis.