Transistors and BJT Fundamentals Flashcards

Vocabulary flashcards covering transistor definitions, BJT operational modes, configurations, parameters, and applications based on Module Three notes.

Transistor

A semiconductor device made of solid pieces of semiconductor material with at least three terminals, used to amplify or switch electronic signals by regulating current or voltage flow.

Base-Emitter Voltage ($V_{BE}$)

The voltage drop that develops between the base and emitter terminals of a transistor while base current exists, depending on the semiconductor material used.

Bipolar Junction Transistor (BJT)

A three-terminal semiconductor device consisting of three layers (base, collector, emitter) of NPN or PNP materials that operates through the movement of both electrons and holes.

Phototransistor

A transistor device featuring a transparent window designed to conduct when exposed to light, using photocurrent generated by photon absorption in the base region as its base current.

Dark Current

The small current that flows in a phototransistor even when no light is present at the base, representing small injected carriers subject to transistor amplification.

Homo-structure Phototransistor

A phototransistor structure with a gain level ranging from $50$ up to a few hundred and a limited bandwidth of $250\text{ kHz}$.

Hetero-structure Phototransistor

A high-gain phototransistor structure with gain up to $10\text{ }000$ and operating frequency limits up to $1\text{ GHz}$, which is costly and rarely used.

Doping

The process of adding very small amounts of selected additives (impurities) to pure semiconductor crystals to increase the number of free charge carriers.

Extrinsic Semiconductor

A semiconductor crystal that has undergone selective doping with either pentavalent donor elements (N-type) or trivalent acceptor elements (P-type).

Leakage Current

The portion of collector current caused by the flow of minority carriers, which is temperature dependent and affects circuit stability at high temperatures.

Common-Emitter (CE) Configuration

A transistor circuit configuration where the emitter terminal is common to both the input (base) and output (collector) circuits.

Common-Base (CB) Configuration

A transistor circuit configuration where the base terminal is common to both the input (emitter) and output (collector) circuits.

Common-Collector (CC) Configuration

A transistor circuit configuration where the collector terminal is common to both the input (base) and output (emitter) circuits.

Cut-off Region

The operating region of a transistor where the base-emitter junction is not forward biased ($V_{BE} < 0.7\text{ V}$), resulting in zero base current ($I_B = 0$) and zero collector current ($I_C = 0$).

Saturation Region

The operating region where the base-emitter junction is forward biased ($V_{BE} > 0.7\text{ V}$), base and collector currents are maximal, collector-emitter voltage $V_{CE}$ is near zero, and the transistor acts as an ON switch.

Active Region

The linear operating region between cut-off and saturation where the emitter-base junction is forward biased and collector-base junction is reverse biased, allowing linear amplification.

Load Line

A straight line plotted on transistor characteristic curves represented by the equation $I_C = \frac{V_{CC} - V_{CE}}{R_C + R_E}$.

Quiescent Point (Q-point)

The operating point selected on the load line that establishes the DC operating current ($I_{CQ}$) and voltage ($V_{CEQ}$) of a biased transistor.

Amplifier

A circuit capable of increasing the input signal level to a higher magnitude by using an active component such as a transistor in common-emitter configuration.

Oscillator

A circuit capable of generating an alternating output signal from a DC source by using fixed feedback from the output with a fundamental loop gain of unity ($1$).