BJT, FET, and Op-Amp Practice Flashcards

Flashcards covering the definitions of BJT and FET regions, amplification factors, MOSFET types, and Operational Amplifier configurations based on lecture notes.

Bipolar

A term indicating that both polarities, electrons and holes, participate in the conduction process.

Junction

Indicates that a BJT has two PN junctions: the Collector-Base (CB) and the Emitter-Base (EB) junctions.

Transistor

A device with a transfer resistance that changes with respect to its region of operation.

BJT Doping Concentration

The relative doping levels in a transistor where Emitter > Collector > Base.

BJT Region Size

The relative physical dimensions of the transistor layers where Collector > Emitter > Base.

Current Controlled Device

A classification for the BJT because the collector current ($I_C$) is controlled by the base current ($I_B$).

Active Region

The operating region where the Emitter-Base junction is forward biased (FB) and the Collector-Base junction is reverse biased (RB), primarily used for amplification.

Saturation Region

The operating region where both the EB and CB junctions are forward biased (FB), allowing the transistor to act as an 'ON' switch.

Cut-off Region

The operating region where both the EB and CB junctions are reverse biased (RB), resulting in no current flow and acting as an 'OFF' switch.

Alpha ($\alpha$)

The common base current gain or amplification factor, defined as the ratio of collector current to emitter current ($I_C / I_E$), typically between $0.95$ and $0.998$.

Beta ($\beta$)

The common emitter current gain, defined as the ratio of collector current to base current ($I_C / I_B$).

Gamma ($\gamma$)

The current amplification factor for the common collector configuration, defined as the ratio of emitter current to base current ($I_E / I_B$).

Early Effect

Also known as base width modulation and named after James and Early, it is the decrease in effective base width caused by an increase in the reverse bias across the Collector-Base junction.

Thermal Runaway

The self-destruction of an unstabilized transistor caused by a continuous cycle where increased temperature leads to higher collector current, which in turn generates more heat.

Stabilization

The process of making the operating point independent of temperature changes and variations in transistor parameters.

Stability Factor ($S$)

The rate of change of collector current ($I_C$) with respect to the leakage current ($I_{CBO}$) when the input voltage and amplification factor are constant.

Field Effect Transistor (FET)

A three-terminal, voltage-controlled, unipolar device that uses an electric field to control current flow between the source and drain.

Pinch-off Voltage ($V_p$)

The specific drain-to-source voltage after which the drain current ($I_D$) becomes constant even if the voltage is increased further.

Enhancement MOSFET (E-MOSFET)

A type of MOSFET that has no conducting channel in its natural state (zero gate bias) and is normally 'OFF'.

Depletion MOSFET (D-MOSFET)

A type of MOSFET that has a conducting channel present in its natural state and is normally 'ON'.

Inversion Layer

The conducting channel formed in a MOSFET when the gate-source voltage exceeds the threshold voltage ($V_{GS} > V_{TO}$).

Drift Current

Current flow caused by the application of an electric field.

Diffusion Current

Current flow caused by a concentration gradient of charge carriers.

Virtual Ground Concept

An Op-Amp principle where the differential input voltage is zero, resulting in identical voltages at both input terminals ($V_A = V_B$).

Inverting Amplifier

An Op-Amp configuration where the output voltage results in a gain of $-\frac{R_f}{R_1}$, causing the output signal to be inverted.

Non-inverting Amplifier

An Op-Amp configuration that provides an output voltage with a gain factor of $(1 + \frac{R_f}{R_1})$.

Buffer Circuit

A configuration where the output voltage is equal to the input voltage ($V_{out} = V_i$).

Feedback Gain ($A_f$)

The gain of a feedback amplifier defined as $A_f = \frac{A}{1 - AB}$.