Practical Electronics Circuits Flashcards
7 cards from real HAM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Practical Electronics Circuits flashcards as text
What is the primary function of a low-noise amplifier (LNA) placed at the front end of a receiver?
Answer: To establish the noise figure of the entire receive chain
The first amplifier in a cascade dominates overall noise figure per Friis's formula, so an LNA with low noise figure minimizes the receiver's noise floor.
In a Colpitts oscillator, the feedback network consists of:
Answer: Two capacitors forming a voltage divider with an inductor
The Colpitts oscillator uses a capacitive voltage divider (two capacitors in series) with an inductor to set frequency and provide feedback.
What does a spectrum analyzer display that a conventional oscilloscope cannot directly show?
Answer: Signal amplitude as a function of frequency
A spectrum analyzer plots amplitude versus frequency, revealing harmonics, spurious outputs, and modulation sidebands that are hidden in a time-domain oscilloscope view.
Which type of logic family typically has the lowest power consumption at low switching frequencies?
Answer: CMOS (complementary MOS)
CMOS draws negligible static current because one transistor in each complementary pair is always off, making it far more power-efficient than bipolar logic families at low frequencies.
What is the purpose of a tank circuit in an RF power amplifier output stage?
Answer: To reconstruct the full RF waveform and filter harmonics
The tank circuit stores energy and resonates at the carrier frequency, restoring the sinusoidal waveform from the amplifier's current pulses and suppressing harmonics.
In a balanced modulator used for DSB-SC generation, what is cancelled at the output?
Answer: The carrier, leaving only the two sidebands
A balanced modulator is designed so the carrier signals from its two halves cancel at the output, producing a double-sideband suppressed-carrier (DSB-SC) signal.
What is the role of a varactor diode in a voltage-controlled oscillator (VCO)?
Answer: To vary the tank circuit capacitance with applied voltage, tuning the frequency
A varactor's junction capacitance changes with reverse bias voltage, allowing electronic tuning of the LC tank circuit resonant frequency.