Chapter 1:
Radio Frequency Amplifier
Contents
 Impedance review
 Series circuit impedance
 Series resonance
 Circuit Q and Bandwidth
 Parallel resonance
 Small signal RF amplifier analysis
 Small signal RF amplifier design
EE 414 Lectures Series By Dr. Muhammad H. Rais
Parallel resonance
Parallel resonant circuit are used when a high impedance, tuned circuit is required.
EE 414 Lectures Series By Dr. Muhammad H. Rais
Parallel Resonance-contd
EE 414 Lectures Series By Dr. Muhammad H. Rais
Parallel Resonance-contd
The impedance gets more and more capacitive: (means capacitor
becomes short circuit) and decreases with 1/f, so that for a
doubling of frequency, the impedance is cut to one-half.
EE 414 Lectures Series By Dr. Muhammad H. Rais
Parallel Resonance-contd
which is inductive.
EE 414 Lectures Series By Dr. Muhammad H. Rais
Parallel Resonance-contd
EE 414 Lectures Series By Dr. Muhammad H. Rais
Nonideal Parallel Resonant Circuits
Inductors used as tuning coils for radio frequency (RF) applications
are usually wound in the form of a solenoid or an a toroid form .
Air core conductors have fairly high Q values; that is, the ratio of
energy stored in the magnetic field to the i2r power lost is high.
The resistive losses occur primarily through wire resistance,
including skin effects at higher frequencies.
Skin effect is the tendency for current to concentrate near the
conductor surface as the frequency is increased.
To reduce the SKIN effect, RF coils are often wound with stranded
wire called Litz wire or hollow tubing for larger current.
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier
Among the myriad uses for tuned networks in communication system, series and
parallel resonant circuit are used at frequencies to reduce the voltage and
current losses that results from series inductance and shunt capacitance.
Series circuits are useful in low impedance UHF power amplifier and microwave
circuits.
Parallel resonance produces high impedance. Below UHF solid state impedances
are high enough.
Shunt capacitance in untuned amplifiers will drastically reduce the gain at high
frequencies  Parallel can restore the gain.
Example  Common emitter amplifier.
Parallel resonating the collector circuit and then transformer coupling to the next
stage.
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier Design
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier Design
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier Design
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier Design
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier Design
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier Design
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier Design
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier Design
EE 414 Lectures Series By Dr. Muhammad H. Rais
Small signal RF Amplifier Design
EE 414 Lectures Series By Dr. Muhammad H. Rais
Coupling Tuned Circuits
EE 414 Lectures Series By Dr. Muhammad H. Rais
Coupling Tuned Circuits
EE 414 Lectures Series By Dr. Muhammad H. Rais
Double Tuned Circuits
EE 414 Lectures Series By Dr. Muhammad H. Rais
Double Tuned Circuits
EE 414 Lectures Series By Dr. Muhammad H. Rais
Double Tuned Circuits
EE 414 Lectures Series By Dr. Muhammad H. Rais
Double Tuned Circuits
EE 414 Lectures Series By Dr. Muhammad H. Rais
Double Tuned Circuits
EE 414 Lectures Series By Dr. Muhammad H. Rais
Double Tuned Circuits
EE 414 Lectures Series By Dr. Muhammad H. Rais