Communications Circuits Flashcards
A passive circuit that variably reduces the amplitude or power of a signal without considerably distorting its waveform
Pad/Attenuator
What do you call fixed attenuators?
Pads
A measure of attenuation introduced by the system in dB
Insertion Loss
It represents the ratio of signal level at one point in a circuit to the signal level at another point in a circuit
Decibel Notation
The decibel originated as Be is named after
Alexander Graham Bell
The impedance which when used to terminate one end of a two-port network will make the impedance seen on the other end equal
Iterative Impedance
Adjusting the source/load impedance
Impedance Matching
It is a frequency-selective circuit designed to pass some frequencies and reject others
Filters
The range of output that have a high output
passband
The range of frequencies that are attenuated or rejected
stopband
The frequency between a passband and a stopband
cut-off frequency
The rate of transition from passband to stopband, and vice versa, is
roll-off rate
The frequency at which the output power is 50% of the maximum or the output amplitude is 70.7% of the maximum
cut-off frequency
Also known as critical frequency, corner frequency, break frequency, and half-power point frequency
cut-off frequency
Composed of only passive components
Passive Filters
A filter that provides no amplification
Passive
Typically employs RC networks and amplifiers with feedback
Active
Termed maximally-flat-magnitude-response filters, optimized for gail flatness in the pass-band and have slow transition.
Butterworth
Optimized for maximally-flat time delay
Bessel
Designed to have a ripple in the passband, but they have a steeper roll-off after the cut-off frequency
Chebyshev
Has an almost perfect frequency response but has variations on both the passband and stopband
Elliptic
Passes freuencies below the cut-off frequency and attenuated those above
Low-Pass Filter
Passes Frequencies above critical frequency but rejects those below
High-Pass Filter
Passes only frequencies in a narrow range between the upper and lower cut-off
Bandpass Filter
Rejects or stops frequencies in a narrow range but passes others.
Bandstop Filter
It is the ratio between the frequencies at two signals
Interval
The condition in an AC circuit where Xl equals Xc
Resonance
It is the basis of all transmitters, receiver, and antenna operation.
Resonant Circuits
Minimum impedance and maximum current happens at
Series resonance
The exchange of energy between the inductor and the capacitor
Flywheel effect
What is the primary purpose of the parallel tuned circuits?
To form a complete AC sine wave output as it produced damped sine wave at resonant frequency.
Maximum Impedance and minimum current
Parallel Resonance
The ratio of the reactive power to the true power
Quality factor
A measure of the band pass filter’s selectivity
Quality Factor
Amplify only a relatively narrow portion of the spectrum, attenuating all other frequencies.
RF Amplifiers
What is the fundamental difference between the AF and RF amplifier?
The band of frequencies they are expected to amplify.
The first stage of an amplifying system showed a low-noise type because all following stages will be amplifying any noise that the system generates.
Power Amplifiers
is biased so that it conducts continuously for 360° of an
input sine wave
Class A
In class A amplifiers, bias is set so that the output ______
never saturates of cuts-off
used primarily as small-signal voltage amplifiers or for low-power amplifiers.
Class A amplifier
biased near cut-off
Class AB
used primarily in push-pull amplifiers
Class AB
biased at cut-off and conducts only one-half of the sine wave input
Class B
Normally connected in a push-pull arrangement so that both positive and negative alternations of the input are amplified simultaneously
Class B
The _______ amplifier, being the most efficient, makes a good power amplifier
Class C
An amplifier whose output conducts load current during less than one-half cycle of an input sine wave
Class C
