ESECE flashcards

35 cards. Read the term and the definition here. The deck at the top of this page is optional.

Thevenin Equivalent

A linear two-terminal network can be replaced by one voltage source V_th in series with one resistance R_th. V_th is the open-circuit port voltage; R_th is found by zeroing independent sources and looking in.

Maximum Power Transfer

A source with fixed Thevenin resistance R_th delivers maximum power to a load when R_L equals R_th. The maximum power is V_th squared divided by four times R_th, at efficiency of 50 percent.

Time Constant RC

For a first-order RC circuit the time constant is tau equals R_th times C. After one tau the response has covered 63.2 percent of its final change; after five tau it is essentially settled.

Series RLC Resonance

At omega zero equal to one over the square root of LC, the series impedance is purely resistive and minimum. The quality factor Q equals omega zero L over R, and bandwidth equals omega zero over Q.

BJT Saturation Region

Both junctions are forward biased, so the collector current no longer equals beta times base current. The collector-emitter voltage collapses to about 0.2 volts, and the device acts as a closed switch.

Transconductance g_m

The small-signal ratio of collector or drain current change to input voltage change. For a BJT, g_m equals I_C divided by V_T, about 26 millivolts at room temperature.

Virtual Short

With negative feedback and ideal op-amp assumptions, the inverting and non-inverting input voltages are forced equal and no current flows into either input. This yields the inverting and non-inverting gain formulas.

Slew Rate

The maximum rate of change of an op-amp output, usually given in volts per microsecond. It limits large-signal bandwidth to slew rate divided by two pi times peak output voltage.

De Morgan's Theorems

The complement of a product equals the sum of the complements, and the complement of a sum equals the product of the complements. They allow any AND-OR expression to be converted to NAND or NOR form.

Karnaugh Map Grouping

Adjacent cells differing in one variable are grouped in powers of two. Groups may wrap across map edges, and the largest possible groups give the minimal sum-of-products expression.

JK Flip-Flop Toggle

When both J and K inputs are high, the output flips to its complement on each active clock edge. With J and K both low the output holds its previous state.

Setup and Hold Time

Setup time is how long data must be stable before the clock edge; hold time is how long it must stay stable after. Violating either causes metastability in the flip-flop.

Convolution Property

Convolution in the time domain corresponds to multiplication in the frequency domain. This is why the output spectrum of an LTI system equals the input spectrum times the frequency response.

Nyquist Sampling Criterion

A bandlimited signal must be sampled at more than twice its highest frequency to be reconstructed without aliasing. Frequencies above half the sampling rate fold back into the baseband.

Region of Convergence

The set of s or z values where the transform integral or sum converges. For a causal stable continuous-time system, the region includes the imaginary axis and lies right of the rightmost pole.

Characteristic Impedance Z0

For a lossless line, Z zero equals the square root of L over C, and the propagation velocity is one over the square root of LC. A load equal to Z zero produces no reflection.

Reflection Coefficient

Gamma equals load impedance minus characteristic impedance, divided by their sum. Its magnitude ranges from zero for a matched load to one for a short or open circuit.

VSWR

The voltage standing wave ratio equals one plus the reflection coefficient magnitude divided by one minus that magnitude. It is one for a perfect match and infinite for a total reflection.

Quarter-Wave Transformer

A line one quarter wavelength long inverts the load impedance, transforming Z_L into Z zero squared over Z_L. It matches a real load when Z zero equals the geometric mean of source and load.

Mass-Action Law

In thermal equilibrium the product of electron and hole concentrations equals the square of the intrinsic carrier concentration. Doping one carrier type reduces the other by the same relation.

Diode Equation

The current is the saturation current times the exponential of voltage over n times thermal voltage, minus one. Thermal voltage is about 26 millivolts at 300 kelvin.

MOSFET Threshold Voltage

The gate-source voltage at which a conducting channel forms. It depends on flat-band voltage, doping, oxide thickness, and temperature, and it falls as temperature rises.

Avalanche Breakdown

Carriers accelerate in a strong field and knock out more carriers, creating a chain multiplication. It has a positive temperature coefficient, so it is the safe region for reverse-biased operation.

Carson's Rule

The bandwidth of an FM signal is approximately twice the sum of peak frequency deviation and the highest modulating frequency. It covers over 98 percent of the signal power.

Friis Noise Formula

Total noise factor of cascaded stages is F one plus (F two minus one) over G one, and so on. The first stage dominates, so a low-noise amplifier is placed at the receiver front end.

Shannon Capacity

Channel capacity in bits per second equals bandwidth times log base two of one plus signal-to-noise ratio. It is an upper bound that no coding scheme can exceed.

PCM Quantization SNR

For a full-scale sinusoid with n-bit uniform quantization, the signal-to-quantization-noise ratio is about 6.02n plus 1.76 decibels. Each extra bit improves it by about 6 decibels.

Routh-Hurwitz Criterion

The number of sign changes in the first column of the Routh array equals the number of right-half-plane poles. It determines stability without solving for the roots.

Phase Margin

Phase margin equals 180 degrees plus the open-loop phase at the gain crossover frequency. It measures relative stability, with 45 to 60 degrees a common design target.

Percent Overshoot

For a second-order underdamped system, overshoot equals 100 times e to the minus zeta pi over the square root of one minus zeta squared. It depends only on the damping ratio.

Vector Table

A table of interrupt handler addresses indexed by interrupt number. On reset the processor loads the initial stack pointer and program counter from its first entries.

Memory-Mapped I/O

Peripheral registers are assigned addresses in the same address space as memory. Ordinary load and store instructions then read and write hardware registers directly.

Per-Unit System

Quantities are expressed as fractions of chosen base values, with Z base equal to V base squared over S base. Transformer ratios disappear, simplifying multi-voltage-level calculations.

Synchronous Speed

The rotating field speed of an AC machine equals 120 times frequency divided by the number of poles. An induction motor runs slightly slower, with slip equal to the speed difference over synchronous speed.

Slip of Induction Motor

Slip equals synchronous speed minus rotor speed, divided by synchronous speed. It is one at standstill, near zero at no load, and rotor frequency equals slip times supply frequency.