1. Tuned Amplifiers
| Term | Definition | Year of Appearance |
|---|---|---|
| Tuned Amplifier | An amplifier designed to amplify a narrow band of radio-frequency signals centered around a resonant frequency, using a high-Q parallel LC tank circuit as its load. | 2025, 2024, 2022, 2021, 2019, 2017 |
| Quality Factor (Q-factor) | The ratio of inductive reactance of a coil at resonance to its winding resistance, which directly determines the sharpness of the resonance curve and the selectivity of the tuned circuit. | 2023, 2022, 2018, 2016, 2015 |
| Selectivity | The ability of a tuned amplifier or receiver to select a desired signal frequency while rejecting all adjacent unwanted frequencies. | Foundational |
| Bandwidth (BW) | The range of frequencies over which the voltage gain of a tuned circuit remains above 70.7% (or 3 dB down) of its maximum gain at resonance. | Foundational |
| Single-Tuned Amplifier | A tuned amplifier configuration that contains only a single parallel LC resonant tank circuit in its collector network to select a specific frequency band. | Foundational |
| Double-Tuned Amplifier | An amplifier that employs two mutually coupled LC tuned circuits (primary and secondary) to achieve a wider, flat-topped bandwidth with steeper roll-off skirts. | Foundational |
| Loose Coupling | A state in double-tuned circuits where the coupling coefficient is small, resulting in a single sharp peak, high selectivity, and narrow bandwidth. | Foundational |
| Tight Coupling | A state where the coupling coefficient is large, reflecting significant impedance between coils, which lowers circuit Q and creates two split peak frequencies. | Foundational |
| Critical Coupling | The optimal degree of coupling at which the maximum possible energy transfer occurs, resulting in a flat-topped frequency response curve. | Foundational |
2. Oscillators
| Term | Definition | Year of Appearance |
|---|---|---|
| Oscillator | An electronic circuit that converts DC power from a supply into AC power at a specific frequency without requiring an external AC input signal. | 2022, 2016, 2015 |
| Sinusoidal Oscillator | An oscillator circuit designed to generate a continuous, low-distortion sine-wave output waveform using RC or LC feedback networks. | 2024, 2023, 2020, 2019 |
| Barkhausen Criterion | The mathematical condition for sustained self-oscillations stating that the loop gain magnitude must be unity (( | A\beta |
| Piezoelectric Crystal | A natural crystal (like quartz) that exhibits the piezoelectric effect, mechanically vibrating when an AC voltage is applied and vice versa, used for highly stable frequency generation. | 2015 |
| Frequency Stability | The ability of an oscillator circuit to maintain a constant, drift-free output frequency over time, despite changes in temperature, load, or supply voltage. | Foundational |
| Piezoelectric Effect | The phenomenon where mechanical stress applied to certain crystals generates an electrical voltage, and conversely, applying an AC voltage causes mechanical vibrations. | Foundational |
| Series Resonance Frequency ((f_s)) | The frequency at which the vibrating crystal’s internal (L-C_s-R) branch acts as a series resonant circuit, offering minimum impedance. | Foundational |
| Parallel Resonance Frequency ((f_p)) | The frequency at which the inductive crystal branch resonates with the external mounting capacitance (C_m), offering maximum impedance. | Foundational |
| Mounting Capacitance ((C_m)) | The equivalent capacitance of a quartz crystal when it is not vibrating, created by its two metal mounting plates separated by the crystal dielectric. | Foundational |
| UJT Relaxation Oscillator | A non-sinusoidal oscillator that uses a Unijunction Transistor (UJT) and an RC charging circuit to produce a periodic sawtooth or pulse output waveform. | Foundational |
3. Feedback Amplifiers
| Term | Definition | Year of Appearance |
|---|---|---|
| Nonlinear Distortion | The distortion that occurs in the large-signal stages of an amplifier due to the non-linear transfer characteristics of active devices, producing unwanted harmonic frequencies. | 2021 |
| Feedback | The process of returning a fraction of an amplifier’s output signal back to its input terminal to modify or control its overall performance. | Foundational |
| Positive Feedback | A feedback mechanism where the returned feedback signal is in-phase with the input signal, aiding it and increasing overall gain at the expense of stability. | Foundational |
| Negative Feedback | A feedback mechanism where the returned feedback signal is (180^\circ) out-of-phase with the input, opposing it to stabilize gain, increase bandwidth, and reduce distortion. | Foundational |
| Feedback Fraction ((\beta)) | The ratio of the feedback signal fed back to the input to the total output signal of the amplifier. | Foundational |
| Loop Gain ((A\beta)) | The product of the basic amplifier’s open-loop gain and the feedback factor, representing the total transmission gain around the closed loop. | Foundational |
| Desensitivity Factor ((1+A\beta)) | The factor ((1+A\beta)) by which the feedback network desensitizes or stabilizes the closed-loop gain against variations in the open-loop gain. | Foundational |
4. Operational Amplifiers (Op-Amps)
| Term | Definition | Year of Appearance |
|---|---|---|
| Operational Amplifier (Op-Amp) | A high-gain, direct-coupled, differential-input integrated circuit amplifier designed to perform a wide variety of analog mathematical operations. | 2024, 2023, 2020, 2017 |
| IC (Integrated Circuit) | A complete electronic circuit containing miniature active and passive components fabricated onto a single silicon semiconductor chip. | 2016 |
| Common-Mode Rejection Ratio (CMRR) | The ability of an op-amp to reject common-mode noise signals, mathematically defined as the ratio of differential voltage gain to common-mode voltage gain. | 2022, 2021, 2018, 2017, 2016 |
| Slew Rate | The maximum rate of change of the op-amp’s output voltage per unit of time, typically expressed in volts per microsecond ((V/\mu s)). | 2022, 2021, 2015 |
| Input Offset Voltage | The small DC voltage that must be applied between the two input terminals of an op-amp to force the output voltage to exactly zero. | 2025, 2023, 2015 |
| Input Offset Current | The algebraic difference between the DC currents flowing into the non-inverting and inverting input terminals of an op-amp under balanced conditions. | 2015 |
| Input Bias Current | The average of the DC currents that flow into the inverting and non-inverting input terminals of an op-amp to bias its internal differential stages. | 2015 |
| Virtual Ground | A circuit condition at the inverting terminal of an ideal op-amp where the terminal voltage is zero (matching the grounded non-inverting input) but no current can enter. | 2017, 2015 |
| Virtual Short | An ideal op-amp state where a voltage short exists between the inverting and non-inverting inputs (keeping their voltages identical), yet the input path remains open to current. | 2017 |
| Integrator Circuit | An op-amp circuit configuration that produces an output voltage proportional to the mathematical integral of the input voltage over time. | 2023 |
| Differentiator Circuit | An op-amp circuit configuration that produces an output voltage proportional to the instantaneous rate of change of the input voltage. | Foundational |
| Power Supply Rejection Ratio (PSRR) | The ratio of the change in input offset voltage to the corresponding change in one of the power supply voltages. | Foundational |
| Common-Mode Gain ((A_{cm})) | The voltage gain of the op-amp when identical signals are applied simultaneously to both input terminals. | Foundational |
| Differential Gain ((A_d)) | The voltage gain of the op-amp for the difference between the two input signals applied to its terminals. | Foundational |
5. Multivibrators and 555 Timers
| Term | Definition | Year of Appearance |
|---|---|---|
| Multivibrator | An electronic circuit containing active components (transistors or logic gates) that can operate in one of three regenerative modes: astable, monostable, or bistable. | 2024, 2023, 2022, 2018, 2017, 2015 |
| Speed-up Capacitor | A small capacitor placed in parallel with the coupling resistor of a switching circuit to accelerate transistor turn-on and turn-off times during transitions. | 2017 |
| Astable Multivibrator | A free-running multivibrator with zero stable states that continuously oscillates between two unstable states, producing a rectangular wave output. | Foundational |
| Monostable Multivibrator | A “one-shot” multivibrator with one stable state that, when triggered, generates a single output pulse of a precisely controlled width before returning to stable. | Foundational |
| Bistable Multivibrator | A multivibrator with two stable states (like a flip-flop) that remains indefinitely in either state until an external trigger forces a state transition. | Foundational |
| Duty Cycle ((D)) | The ratio of the active high pulse duration to the total time period ((T)) of a periodic wave, typically expressed as a percentage. | Foundational |
6. Filters
| Term | Definition | Year of Appearance |
|---|---|---|
| Order of Filter | The number of reactive components (capacitors or inductors) in a filter, which determines the rate of roll-off (slope) in its stopband. | 2023, 2019, 2017, 2016, 2015 |
| Filter | A frequency-selective circuit that allows signals within a specified frequency band (passband) to pass while attenuating signals in other bands (stopband). | 2024 |
| Cut-off Frequency ((f_C)) | The boundary frequency at which the output voltage gain of a filter drops to 70.7% (-3 dB) of its maximum passband value. | 2017, 2016 |
| Transition Time | The time taken by a filter output or a switching circuit to transition from one defined logic or voltage state to another. | 2015 |
| Settling Time | The time required for an output signal to enter and remain within a specified error band around its final steady-state value following a transient. | 2015 |
| Symmetrical Triggering | A triggering method where identical trigger pulses of the same polarity are used to alternate states in a multivibrator. | 2015 |
| Unsymmetrical Triggering | A triggering method where separate trigger inputs of different polarities or applied to different points are used to initiate state changes. | 2015 |
| Notch Filter | A band-reject filter designed to highly attenuate a very narrow band of frequencies while passing all frequencies above and below this band. | 2015 |
| 20 dB/decade (and 40 dB/decade) | Standard units measuring filter stopband roll-off rate, where 20 dB/decade represents a tenfold reduction in signal amplitude for every tenfold increase in frequency. | 2018 |
| Active Filter | A filter circuit that uses active components (like op-amps) in addition to resistors and capacitors to provide frequency selection with power gain and no loading effects. | Foundational |
| Passband | The range of input frequencies that are allowed to pass through a filter circuit with minimum attenuation. | Foundational |
| Stopband | The range of input frequencies that are highly attenuated or blocked by a filter circuit. | Foundational |
| Butterworth Approximation | A filter design approach (maximally flat) characterized by a flat passband frequency response and a monotonic roll-off in the stopband. | Foundational |
7. Wave Shaping Circuits
| Term | Definition | Year of Appearance |
|---|---|---|
| Comparator | An op-amp circuit operating in open-loop that compares an input voltage with a reference voltage, switching its output to (+V_{sat}) or (-V_{sat}) based on which is larger. | 2024, 2023 |
| Schmitt Trigger | A comparator circuit with positive feedback that exhibits hysteresis, switching output states only when the input exceeds specific upper and lower threshold points. | 2020, 2017, 2015 |
| Clipper (Clipping Circuit) | A wave-shaping circuit that uses diodes and biasing sources to cut off or remove portions of an input signal waveform above or below a specified level. | 2021, 2020, 2019, 2016, 2015 |
| Clamper (Clamping Circuit) | A circuit consisting of a diode, capacitor, and resistor that shifts a waveform to a different DC level without changing its shape or peak-to-peak amplitude. | 2021, 2020, 2019, 2018 |
| Hysteresis Voltage ((V_H)) | The difference between the upper threshold voltage (UTP) and the lower threshold voltage (LTP) of a Schmitt trigger, which provides immunity to input noise. | Foundational |
| Upper Threshold Point (UTP) | The positive-going input voltage level at which a Schmitt trigger’s output switches from (+V_{sat}) to (-V_{sat}) (or vice-versa). | Foundational |
| Lower Threshold Point (LTP) | The negative-going input voltage level at which a Schmitt trigger’s output switches back to its opposite saturation state. | Foundational |
| Window Comparator (Limit Detector) | A comparator circuit containing two threshold levels that detects whether an unknown input voltage lies within or outside a specified voltage “window”. | Foundational |
8. Phase Locked Loop (PLL)
| Term | Definition | Year of Appearance |
|---|---|---|
| Phase Locked Loop (PLL) | A closed-loop feedback control system containing a phase detector, low-pass filter, error amplifier, and VCO that synchronizes an output frequency with an input frequency. | 2023, 2022, 2018, 2017, 2016, 2015 |
| Lock-in Range | The range of input frequencies over which a PLL, once locked on to an input signal, can successfully track and maintain its frequency synchronization with the input. | Foundational |
| Capture Range | The range of input frequencies within which a free-running PLL can initially acquire lock-in and establish frequency synchronization with an incoming signal. | Foundational |
| Free Running Frequency ((f_o)) | The self-oscillating output frequency of the PLL’s Voltage-Controlled Oscillator (VCO) when no input signal is applied to the loop. | Foundational |
| Voltage Controlled Oscillator (VCO) | An oscillator circuit whose output oscillation frequency is directly and linearly controlled by an input DC control voltage. | Foundational |
Extras
2. Oscillators
| Term | Definition | Year of Appearance / Source |
|---|---|---|
| Intrinsic Stand-off Ratio ((\eta)) | The ratio of internal base resistance (R_{B1}) to the total inter-base resistance (R_{BB}) of a Unijunction Transistor (UJT) under open-emitter conditions, which determines its peak-point firing voltage ((V_P = \eta V_{BB} + V_D)). | Foundational (Surrounds UJT PYQs: 2025, 2022, 2017) |
3. Feedback Amplifiers
| Term | Definition | Year of Appearance / Source |
|---|---|---|
| Swamping | A design technique of connecting a relatively large external resistance in series with a semiconductor junction to make its temperature-sensitive internal AC resistance ((r’_e)) negligible, thereby stabilizing voltage gain. | Foundational (Swamped Amplifiers, Malvino Ch. 8/17) |
4. Operational Amplifiers (Op-Amps)
| Term | Definition | Year of Appearance / Source |
|---|---|---|
| Gain-Bandwidth Product (GBW) | The constant product of an op-amp’s closed-loop voltage gain and its operating bandwidth, which equals its unity-gain frequency ((f_{unity})). | Foundational (Surrounds Op-Amp parameter PYQs: 2020, 2017, 2015) |
| Thermal Drift | The average rate of change of an op-amp’s input offset voltage, input offset current, or input bias current per unit change in temperature, denoted as (\Delta V_{io}/\Delta T). | Foundational (Gayakwad Ch. 4) |
| Long-Tail Pair | A differential amplifier configuration consisting of two matched transistors sharing a common emitter bias resistor (“long tail”) designed to reject common-mode noise while amplifying differential signals. | Foundational (Surrounds Diff-Amp PYQs: 2018, 2016) |
5. Multivibrators and 555 Timers
| Term | Definition | Year of Appearance / Source |
|---|---|---|
| Pulse-Width Modulation (PWM) | A modulation technique where the width of rectangular output pulses is varied proportionally to the instantaneous amplitude of an analog modulating input, while the period remains constant. | Foundational (Surrounds 555 Timer Applications, Malvino Ch. 21) |