Chapter 2: Radio-Frequency Circuits

The time it takes a charge carrier to cross from the emitter to the collector is called: a. base time c. charge time b. transit time d. Miller time

B

A real capacitor actually contains: a. capacitance and resistance only c. capacitance, inductance, and resistance b. capacitance and inductance only d. reactance only

C

Bypass capacitors are used to: a. remove RF from non-RF circuits c. neutralize amplifiers b. couple RF around an amplifier d. reduce the Miller effect

A

A resonant circuit is: a. a simple form of bandpass filter c. both a and b b. used in narrowband RF amplifiers d. none of the above

C

"Loading down a tuned-circuit amplifier will: a. raise the Q of the tuned circuit c. ""multiply"" the Q b. lower the Q of the tuned circuit d. have no effect on Q"

B

"The ""Miller Effect"" can: a. cause an amplifier to oscillate c. reduce the bandwidth of an amplifier b. cause an amplifier to lose gain d. all of the above"

D

The Miller Effect can be avoided by: a. using a common-emitter amplifier c. increasing the Q of the tuned circuit b. using a common-base amplifier d. it cannot be avoided

B

In a BJT, the Miller Effect is due to: a. inductance of collector lead c. base-to-emitter capacitance b. collector-to-emitter capacitance d. base-to-collector capacitance

D

In RF amplifiers, impedance matching is usually done with: a. RC coupling c. direct coupling b. transformer coupling d. lumped reactance

B

"Neutralization cancels unwanted feedback by: a. adding feedback out of phase with the unwanted feedback b. bypassing the feedback to the ""neutral"" or ground plane c. decoupling it d. none of the above"

A

"For a ""frequency multiplier"" to work, it requires: a. a nonlinear circuit b. a linear amplifier c. a signal containing harmonics d. an input signal that is an integer multiple of the desired frequency"

A

A sinusoidal oscillation from an amplifier requires: a. loop gain equal to unity b. phase shift around loop equal to 0 degrees c. both a and b, but at just one frequency d. none of the above

C

The conditions for sinusoidal oscillation from an amplifier are called: a. the loop-gain criteria c. the Bode criteria b. the Hartley criteria d. the Barkhausen criteria

D

The Hartley oscillator uses: a. a tapped inductor c. an RC time constant b. a two-capacitor divider d. a piezoelectric crystal

B

The Colpitts VFO uses: a. a tapped inductor c. an RC time constant b. a two-capacitor divider d. a piezoelectric crystal

B

The Clapp oscillator is: a. a modified Hartley oscillator c. a type of crystal-controlled oscillator b. a modified Colpitts oscillator d. only built with FETs

B

A varactor is: a. a voltage-controlled capacitor c. used in tuner circuits b. a diode d. all of the above

D

Crystal-Controlled oscillators are: a. used for a precise frequency b. used for very low frequency drift (parts per million) c. made by grinding quartz to exact dimensions d. all of the above

D

If two signals, Va = sin(ωat) and Vb = sin(ωbt), are fed to a mixer, the output: a. will contain ω1 = ωa + ωb and ω2 = ωa - ωb b. will contain ω1 = ωa / ωb and ω2 = ωb / ωa c. will contain ω = (ωa + ωb ) / 2 d. none of the above

A

In a balanced mixer, the output: a. contains equal (balanced) amounts of all input frequencies b. contains the input frequencies c. does not contain the input frequencies d. is a linear mixture of the input signals

C

"""VFO"" stands for: a. Voltage-Fed Oscillator c. Varactor-Frequency Oscillator b. Variable-Frequency Oscillator d. Voltage-Feedback Oscillator"

B

"A ""frequency synthesizer"" is: a. a VCO phase-locked to a reference frequency b. a VFO with selectable crystals to change frequency c. a fixed-frequency RF generator d. same as a mixer"

A