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MECA Electronics

Module 8 - Introduction to Amplifiers
Navy Electricity and Electronics Training Series (NEETS)
Chapter 2:  Pages 2-31 through 2-35

COMBINATION PEAKING is accomplished by using both series and shunt peaking.
 

COMBINATION PEAKING

 
LOW-FREQUENCY COMPENSATION is accomplished in a video amplifier by the use of a parallel RC circuit in series with the load resistor.
 

LOW-FREQUENCY COMPENSATION

 

2-31


A RADIO-FREQUENCY (RF) AMPLIFIER uses FREQUENCY-DETERMINING NETWORKS
to provide the required response at a given frequency.
 

RADIO-FREQUENCY (RF) AMPLIFIER

 
The FREQUENCY-DETERMINING NETWORK in an RF amplifier provides maximum impedance at the desired frequency. It is a parallel LC circuit which is called a TUNED CIRCUIT
 

FREQUENCY-DETERMINING NETWORK

 
TRANSFORMER COUPLING is the most common form of coupling in RF amplifiers. This coupling is accomplished by the use of RF transformers as part of the frequency-determining network for the amplifier.
 

TRANSFORMER COUPLING

2-32


ADEQUATE BANDPASS is accomplished by optimum coupling in the RF transformer or by the use of a SWAMPING RESISTOR.
 
NEUTRALIZATION in an RF amplifier provides feedback (usually positive) to overcome the effects caused by the base-to-collector interelectrode capacitance.
 

NEUTRALIZATION

 
 

ANSWERS TO QUESTIONS Q1. THROUGH Q42.

 
A-1.   The difference between the upper and lower frequency limits of an amplifier.
 
A-2.   The half-power points of a frequency-response curve. The upper and lower limits of the band f frequencies for which the amplifier is most effective.
 
A-3.   (A) f2  = 80 kHz, f1  = 30 kHz, BW = 50 kHz (B) f2  = 4 kHz, f1  = 2 kHz, BW = 2 kHz
 
A-4.   The capacitance and inductance of the circuit and the interelectrode capacitance of the transistor.
 
A-5.   Negative (degenerative) feedback.
 
A-6.   It decreases.
 
A-7.   It increases.
 
A-8.   The capacitance of the circuit.
 
A-9.    Peaking coils.
 
A-10.   The relationship of the components to the output-signal path.
 
A-11.   Combination peaking.
 
A-12.   The coupling capacitor (C3).
 

2-33


A-13.   A shunt peaking coil for Q2.
 
A-14.   A decoupling capacitor for the effects of R2.
 
A-15.   A part of the low-frequency compensation network for Q1.
 
A-16.   A series peaking coil for Q1.
 
A-17.   A swamping resistor for L2.
 
A-18.   L1, L2, and R5.
 
A-19.   R9 and C5.
 
A-20.   The gain increases.
 
A-21.   The gain decreases.
 
A-22.   To provide maximum impedance at the desired frequency.
 
A-23.   Yes.
 
A-24.   By changing the value.
 
A-25.   Transformer coupling.
 
A-26.   It uses fewer components than capacitive coupling and can provide an increase in gain.
 
A-27.   A step-down transformer.
 
A-28.   A too-narrow bandpass.
 
A-29.   By using an optimally-coupled transformer.
 
A-30.   Low gain at the center frequency.
 
A-31.   A swamping resistor in parallel with the tuned circuit.
 
A-32.   RF transformers are used and the transistor is neutralized.
 
A-33.   Degenerative or negative.
 
A-34.   By neutralization such as the use of a capacitor to provide regenerative (positive) feedback.
 
A-35.  C2 and the secondary of T1.
 
A-36.   R1 provides the proper bias to the base of Q1 from VBB.
 
A-37.   R2 provides the proper bias to the emitter of Q1.
 
A-38.   The output would decrease. (C4 decouples R2 preventing degenerative feedback from R2.)
 
A-39.    C5 and the primary of T2.
 
A-40.   Four.

2-34


A-41.   The dotted lines indicate that these capacitors are "ganged" and are tuned together with a single control.
 
A-42.   C3 provides neutralization for Q1.

2-35



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