Module Three: Transistors Flashcards

Practice flashcards covering definitions, structures, and operating regions of transistors and phototransistors.

Transistor

A semiconductor device commonly used to amplify or switch an electronic signal by regulating current or voltage flow.

Base-emitter voltage ($V_{BE}$)

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

Bipolar Junction Transistors (BJTs) and Field-Effect Transistors (FETs)

The two major groups into which transistors are divided.

Bipolar Junction Transistor (BJT)

A three-terminal device (base, collector, and emitter) constructed as a combination of two diodes connected back to back.

Phototransistor

A BJT designed to conduct upon exposure to light, where the absorption of photons in the large base region generates a photocurrent acting as base current.

Homo-structure phototransistor

A type of phototransistor with a gain level from 50 up to a few hundred and a limited bandwidth of $250\,kHz$.

Hetero-structure phototransistor

A costly phototransistor structure with a gain level up to ten thousand and operating frequencies as high as $1\,GHz$.

Dark current

The small current that flows in a phototransistor even when no light is present, representing carriers injected into the emitter and amplified by transistor action.

NPN Transistor

A BJT construction featuring two large N-type semiconductor materials separated by a thin P-type semiconductor material in the middle.

PNP Transistor

A BJT construction featuring two P-type materials separated by a thin N-type material in the center.

Doping

The process of adding small amounts of selected impurities to semiconductor crystals to increase the number of free charges.

Extrinsic semiconductors

Semiconductors doped as either N-type (using pentavalent donor elements) or P-type (using trivalent acceptor elements).

Common-Emitter (CE) Configuration

A transistor circuit configuration where the emitter is common to both input and output, providing a phase angle of $180^o$ and very high power gain.

Common-Base (CB) Configuration

A configuration where the base is common to the emitter and collector, characterized by low input impedance and high voltage gain.

Common-Collector (CC) Configuration

A configuration where the collector is common to both base and emitter, offering high input impedance, low output impedance, and high current gain.

Cut-off region

An operating region where the base-emitter junction is not forward biased, $I_B = 0$, $I_C = 0$, $V_{BE} < 0.7\,V$, and the transistor is off.

Saturation region

An operating region where the base-emitter junction is forward biased, $I_B$ and $I_C$ are maximal, $V_{BE} > 0.7\,V$, and the transistor is on with $V_{CE} = 0$.

Active region

The region between cut-off and saturation where the emitter-base junction is forward biased, the collector-base is reverse biased, and the transistor acts as an amplifier.

Quiescent (Q) point

The operating point selected on the load line where the values of the operating point current ($I_{CQ}$) and voltage ($V_{CEQ}$) are located.

Amplifier

A circuit that uses a transistor as an active component to increase an input signal level to a higher magnitude.

Oscillator

A circuit that provides an alternating output from a DC source, maintained by fixed feedback where the loop gain must be unity (1).

Kirchhoff’s current law for transistors

The relationship stating that the emitter current is the sum of both collector and base currents: $I_E = I_B + I_C$.

Operational Amplifier (Op-Amp)

A high-gain voltage amplifier with a differential input and a single-ended output used in various applications such as signal conditioning, filtering, and mathematical operations.

Input Impedance

The impedance seen by a signal at the input terminals of a circuit, which can affect the signal strength and performance of the overall circuit.

Gain

The ratio of output signal power to the input signal power, expressed as a dimensionless number or in decibels (dB). Higher gain means a stronger output signal.

Feedback

The process of returning a portion of the output signal back to the input to control the gain, stability, and bandwidth of the amplifier circuit.

Voltage Divider

A simple circuit that produces an output voltage that is a fraction of the input voltage, commonly used in applications requiring lower voltage signals.

Bypass Capacitor

A capacitor connected in parallel with a power supply line to provide a local energy reservoir and filter out noise in an electronic circuit.

Signal-to-Noise Ratio (SNR)

A measure of signal strength relative to background noise, typically expressed in decibels (dB), indicating the quality of the signal.

Rise Time

The time taken for a signal to change from a specified low value to a specified high value, crucial in assessing the speed of response of a circuit.

Fall Time

The time taken for a signal to change from a specified high value to a specified low value, important for determining circuit performance in digital applications.

Power Amplifier

An amplifier designed to deliver high output power to a load, typically used in audio and RF applications to drive speakers or antennae.

Integrated Circuit (IC)

A set of electronic circuits on a small chip made of semiconductor material, used to perform various functions in electronic devices.

Hysteresis

The lag between input and output in a system when the input signal is cycled, often seen in control systems and switching circuits to improve stability and reduce noise.

Transistor

A semiconductor device commonly used to amplify or switch an electronic signal by regulating current or voltage flow.

Base-emitter voltage ($V_{BE}$)

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

Bipolar Junction Transistors (BJTs) and Field-Effect Transistors (FETs)

The two major groups into which transistors are divided.

Bipolar Junction Transistor (BJT)

A three-terminal device (base, collector, and emitter) constructed as a combination of two diodes connected back to back.

Phototransistor

A BJT designed to conduct upon exposure to light, where the absorption of photons in the large base region generates a photocurrent acting as base current.

Homo-structure phototransistor

A type of phototransistor with a gain level from 50 up to a few hundred and a limited bandwidth of $250\,kHz$.

Hetero-structure phototransistor

A costly phototransistor structure with a gain level up to ten thousand and operating frequencies as high as $1\,GHz$.

Dark current

The small current that flows in a phototransistor even when no light is present, representing carriers injected into the emitter and amplified by transistor action.

NPN Transistor

A BJT construction featuring two large N-type semiconductor materials separated by a thin P-type semiconductor material in the middle.

PNP Transistor

A BJT construction featuring two P-type materials separated by a thin N-type material in the center.

Doping

The process of adding small amounts of selected impurities to semiconductor crystals to increase the number of free charges.

Extrinsic semiconductors

Semiconductors doped as either N-type (using pentavalent donor elements) or P-type (using trivalent acceptor elements).

Common-Emitter (CE) Configuration

A transistor circuit configuration where the emitter is common to both input and output, providing a phase angle of $180^o$ and very high power gain.

Common-Base (CB) Configuration

A configuration where the base is common to the emitter and collector, characterized by low input impedance and high voltage gain.

Common-Collector (CC) Configuration

A configuration where the collector is common to both base and emitter, offering high input impedance, low output impedance, and high current gain.

Cut-off region

An operating region where the base-emitter junction is not forward biased, $I_B = 0$, $I_C = 0$, V_{BE} < 0.7\,V, and the transistor is off.

Saturation region

An operating region where the base-emitter junction is forward biased, $I_B$ and $I_C$ are maximal, V_{BE} > 0.7\,V, and the transistor is on with $V_{CE} = 0$.

Active region

The region between cut-off and saturation where the emitter-base junction is forward biased, the collector-base is reverse biased, and the transistor acts as an amplifier.

Quiescent (Q) point

The operating point selected on the load line where the values of the operating point current ($I_{CQ}$) and voltage ($V_{CEQ}$) are located.

Amplifier

A circuit that uses a transistor as an active component to increase an input signal level to a higher magnitude.

Oscillator

A circuit that provides an alternating output from a DC source, maintained by fixed feedback where the loop gain must be unity (1).

Kirchhoff’s current law for transistors

The relationship stating that the emitter current is the sum of both collector and base currents: $I_E = I_B + I_C$.

Operational Amplifier (Op-Amp)

A high-gain voltage amplifier with a differential input and a single-ended output used in various applications such as signal conditioning, filtering, and mathematical operations.

Input Impedance

The impedance seen by a signal at the input terminals of a circuit, which can affect the signal strength and performance of the overall circuit.

Gain

The ratio of output signal power to the input signal power, expressed as a dimensionless number or in decibels (dB). Higher gain means a stronger output signal.

Feedback

The process of returning a portion of the output signal back to the input to control the gain, stability, and bandwidth of the amplifier circuit.

Voltage Divider

A simple circuit that produces an output voltage that is a fraction of the input voltage, commonly used in applications requiring lower voltage signals.

Bypass Capacitor

A capacitor connected in parallel with a power supply line to provide a local energy reservoir and filter out noise in an electronic circuit.

Signal-to-Noise Ratio (SNR)

A measure of signal strength relative to background noise, typically expressed in decibels (dB), indicating the quality of the signal.

Rise Time

The time taken for a signal to change from a specified low value to a specified high value, crucial in assessing the speed of response of a circuit.

Fall Time

The time taken for a signal to change from a specified high value to a specified low value, important for determining circuit performance in digital applications.

Power Amplifier

An amplifier designed to deliver high output power to a load, typically used in audio and RF applications to drive speakers or antennae.

Integrated Circuit (IC)

A set of electronic circuits on a small chip made of semiconductor material, used to perform various functions in electronic devices.

Hysteresis

The lag between input and output in a system when the input signal is cycled, often seen in control systems and switching circuits to improve stability and reduce noise.