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RF Workbench  (shareware) # Module 8 - Introduction to AmplifiersNavy Electricity and Electronics Training Series (NEETS)Chapter 2:  Pages 2-31 through 2-35

Module 8 − Introduction to Amplifiers

Pages i, 1−1, 1−11, 1−21, 1−31, 2−1, 2−11, 2−21, 2−31, 3−1, 3−11, 3−21, 3−31, 3−41, 3−51, 3−61, AI−1, Index

 NEETS Modules - Matter, Energy, and Direct Current - Alternating Current and Transformers - Circuit Protection, Control, and Measurement - Electrical Conductors, Wiring Techniques, and Schematic Reading - Generators and Motors - Electronic Emission, Tubes, and Power Supplies - Solid-State Devices and Power Supplies - Amplifiers - Wave-Generation and Wave-Shaping Circuits - Wave Propagation, Transmission Lines, and Antennas - Microwave Principles - Modulation Principles - Introduction to Number Systems and Logic Circuits - - Introduction to Microelectronics - Principles of Synchros, Servos, and Gyros - Introduction to Test Equipment - Radio-Frequency Communications Principles - Radar Principles - The Technician's Handbook, Master Glossary - Test Methods and Practices - Introduction to Digital Computers - Magnetic Recording - Introduction to Fiber Optics Note: Navy Electricity and Electronics Training Series (NEETS) content is U.S. Navy property in the public domain.

Combination Peaking is accomplished by using both series and shunt peaking. Low-Frequency Compensation is accomplished in a video amplifier by the use of a parallel RC circuit in series with the load resistor. 2-31

A Radio-Frequency (RF) Amplifier uses Frequency-Determining NetworkS

to provide the required response at a given frequency. 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 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. 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. 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).

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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.

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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.

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