Scholars' Mine Masters Theses Student Theses and Dissertations 1960 Design of an intermediate frequency amplifier and ariablev frequency oscillator Robert Charles McIntyre Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Electrical and Computer Engineering Commons Department: Recommended Citation McIntyre, Robert Charles, "Design of an intermediate frequency amplifier and ariablev frequency oscillator" (1960). Masters Theses. 2668. https://scholarsmine.mst.edu/masters_theses/2668 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. / ~.r.,..,. l ::> (ff DESIGN OF AN INTERMEDIATE FREQUENCY, AMPLIFIER AND VARIABLE FREQUENCY OSCILLATOR BY ROBERT CHARLES MCINTYRE A THESIS · -s~bmi tted to the faculty of the SCHOOL OF MINES AND METALLURGY OF THE UNIVERSITY OF MISSOURI in partial fulfillment of the work required for the Degree of MASTER OF SCIENCE IN ELECTRICAL ENGINEERING Rolla, !'11 ssouri _ 1960 Approved by ii ACKNOWLEDGEMENT The author wishes to acknowledge the_guidanc~ and as­ sistance give1:1 him by Doctor Roger E. ·Nolte, and Professor . Robert H. Nau, of the Electrioal·Engineering Department. i.ii TABLE OF·CONTENTS CHAPTER PAGE I. THE PROBLEM ••••• -••••••••••••••••••••••••••• o o ••• • 1 A. INTRODUCT·ION ••••••• ·•••••••••••••••• .--• • • • • • • • • 1 B. THE PROBLEM •••••••••••••· •• -.................... 1 Co THE SCOPE OF THE INVESTIGATION •••••••••• ~ •••• 3 D. REVIEW OF LITERATURE ••••••••••••••••••••••••• 3 E. ORGANIZATION OF THE REMAINDER OF THE THESIS •• 4 . II. NEUTRALIZATION OF THE TRANSISTOR AMPLIFIER....... 5 A. INTRODUCTION... • • • • • • • • • • • • • • • • • • • •.• • • • • • • • • • ·5 B. THEORY OF NEUTRALIZATION ••••••••••••••••••••• 5 C. EXPERIMENTAL DETEHMIMATION .OF THE NEUTRALIZING.CAPACITANCE •••••••••••••••••••• 11 III. INPUT AND OUTPUT IMPEDANCE DETERMINATION ••••••••• 1.5 A~ INTRODUCTION ••••••••••••••••••••••••••••••••• 1.5 B. THEORETICAL ANALYSIS OF INPUT. AND OUTPUT IMPEDANCES •••• ~•••••••••••••••••••••• 16 C. EXPERIMENTAL DETERMINATION.· .OF --INP-µT AND OUTPUT IMPEDANCE •••••••• o o <' o o o o •••••- • • • • . • • • • 18 N. BIAS NETWORK DESIGN ••••• -. •••• ·• •••••••••••: . • • • • • • • 24 A. INTRO DUCT ION •••• ~ ••••••••• ~ •.••••• ~ • • • • • • • • • • •. 24 B. DESIGM CONSIDERATIONS •••••••••••••••••• .- • • • • • 26· C. DESIGM OF THE BIAS NETWORK ••••• ~ ••••••••••••• ·29- D~ &"'a'ERIHENTAL ;RESULTS ••• ·•••••••••••••••••••••• 32 V. DESIGN OF COUPLING NETWORKS •••••••• ·••••• ~ • • • • • • • • 36 A. INTRODUCTION •••••••••••••• ;~ ••••.•... •.• • • • • • • • 36 iv CHAPTER PAGE B. DESIGM OF SI1!GLE TUNED STAGES............. 41 VI. AMPLIFIER GAIN ••• ~ •••••••••••••.••••••••••• ~ • • • • l~7 A. INTRODUCTION' ••••••.•• !...................... 47 B; CONSTRUCTION •••••••••••••.•.~ ••••••••.••••.• o. 48 c. EVALUATION OF THE GAIN ••••••• •.• •.••••• o ••• o. 51 VII. THE VARIABLE FREQUENCY·OSCILLATOR •••••••••• o••• 55 A. INTRQD~CTION••••••••••••••••••••••••••••••• 55 B. DESIGN .OF .10. MC VARIABLE FREQUENCY OSCILLATOR •••••••••••••••••••••••• ~.oo•••• .5.5 VIII.· SUGGESTIONS·FOR ADDITIONAL INVESTIGATION ••••••• 63 BIBLIOGRAPHY •••••• oo•••······························· 65 APPE1'..Ti) IX I 0 • e • 0 • 0 0 0 0 o e e O O O O • •·• 0 0 0 e O O • 0 0 • 0 0 0 0 e O O O O O O O O 66 f,.PPEIIDIX II •••••••••••• ;. o... ... 70 VITA••••••••••••••••••••••••••••••••••o••••••••••••••• 72 v LIST OF TABLES TABLE PAGE · I. NEUTRALIZING CAPACITANCE •••••••••••• •............ 13 II. INPUT AND OUTPUT IMPEDANCE .OF THE 2N1271 WITH .FREQUENCY AS THE VARIABLE •••••••••••••••••• 21 III. COLLECTOR CURRENT VERSUS TEMPERATURE ••••••••••••• 35 Dl. COEFFICIENT OF COUPLING •••••••••••••••••••••••••• 44 V. OUTPUT VOLTAGE VERSUS FREQUENCY ••••••.•••••••••••• 45 VT. POWER GAIN PER STAGE••••••••••••••••••••••. ·••••••• 51 vi LIST OF FIGURES FIGURES PAGE 1. TRANSISTOR TERMINAL VOLTAGES AND CURRENTS •••••••••• 7 2. HIGH FREQUENCY EQUIVALENT CIRCUIT •••••••••••••••••• 10 3. A BRIDGE' NEUTRALIZED CIRCUIT ••••••••••••••••••••••• 10 4. NEUTRALIZATION OF THE TRANSISTOR••••••••••••••••••• 12 5. THE BASE TO EMITTER VOLTAGES••••••••••••••••••••••• 12 6. DETERMINATION OF OUTPUT IMPEDANCE •••••••••••••••••• 23 7. TRANSISTOR CURRENTS ••••••••••••••••••••••.•••••••••• 25 8. TYPICAL GROUNDED EMITTER. STAGE••••••••••••••••••••• 27 9. BIAS CIRCUIT••••••••••••••••••••••••••••••••••••••• 32 10. TEMPERATURE VERSUS COLLECTOR CURRENT ••••••••••••••• 34 11. COUPLING NETvlORK • •••••••••••••••••••••••••••••••••• 40 12. OUTPUT VOLTAGE OF AMPLIFIER VERSUS FREQUENCY ••••• ~. 46 13. 10 MC AMPLIFIER STRIP•••••••••••••••••••••••••••••• 49 14. ASSEMBLED UNITS•••••••••••••••••••••••••••••••••••• 50 15. GENERAL FEEDBACK CIRCUIT••••••••••••••••••••••••••• .55 16. HIGH FREQUENCY OSCILLATOR •••••••• !t· ••••••••••• -•••••• 56 - 17. GENERAL FEEDBACK DIAGRAM •••••••••••- •••••••••••••••• 56 18. FEEDBACK NET't-lORK ••••••••••••••••• ~ •• • ••• • •••••••••• 57 19. APPROXIMATE FEEDBACK NETWORK •••••• "•••••••••••••••• 58 20. NEUTRALIZING NETWORK ••••••• •-• •••••••••••••• •• •••••• .66 21. TRANSISTOR EQUIVALENT CIRCUIT•••••••••••••••••••••• 67 22. TRANSISTOR EQUIVALENT CIRCUIT. • • • • • • .• • • • • • • • • • • • • • • 70 vii .LIST OF .SDIBOLS A Amplification c ·capacitance c Collector­ db Decibe'i e·1 . Ac input voltage AC output voltage Frequency Frequency at which \od is reduced _by· 3 db Power -Gain g1 ---- Inp~t conductance Output qonduct~ce Hybrid _parameters DC current IB DC base current IC ---- DC collector current I Collector cur·rent with ·collector junction reversed CC:}O biased ·and base open ciroui'ted~ · · I Collector junction is. reversed·biased ·and · emitter coo is de open circuited.; I Same as above co IE DC ,emitter current i AC ,current i AC . ba·se current. b i AC co. llector current ·c ic ·---- AC emitter current vi'ii i . ---- AC output current 0 i. J. Network currents j K A fraction L Inductanqe M Mutual. in~uctance M N type semiconductor material p Ppwer Q Ratio of reactance to resistance ---·- ·Resistance Exte~nal base res:Lstance Ex~er~ai. emitter resistance Generator resistance Equivaient base resistance B~~e spre~ding resistance. r --.-.-.· Eq-µ.~valent · colleqtor resistanc~ c r • Emitter diffusion resis·tanc·e e StaJ:~iii ty facto~ Collector b~as voltage C~paG~tive rea9t~nce -~ Iµ~uctiye reactance Y - Aa.mittanqe Yi ·· --~- S~9rt ci~cuit parameters Z I~pe~a~ce . z. ---- Open . ci~cui t ~mpedance parameters ]. ix GREEK LETTER SYMBOLS ol Short circuit current amplification fa~tor ~ Current amplification of feedback network A~--~- Bandwidth 17 Efficiency . lT Number of radians equivalent to 180° /JI A.i.igular frequency CHAPTER I THE PROBLEM A. INTRODUCTION Since the advent of_ the . transistor in 1948 many ~ec_J::i:­ nological barriers have be~n overco~e in the field of semi­ c_onductors. Unfo.rtunately, however, there is a considerable. period of time between the discovery of a scientific phenom­ ena and i -t;;s widespread use and tmders:tanding by practicing engineers. The motiva~ing factor which pro~pted this inves­ tigation was primari:;t.y the lack.of knowledge whic1:1, the author possessed concering transistors. The selection of the ampli­ fier and oscillator design confined.J the study, primarily• . • to the transistor. Considerable_ time, holAfever, had _to be spent in the study of basic transi~tor theory before any phase of the de_sign could be effected.· B., THE- PROBLEM Statement gL.pr~blem~· This st~dy was . unde!.'ta~en to · · investigate·. .the theoretical _and p;r-ac_t~cal appli~~:tion of. the trans_istor . in a bap.d p~ss amplifter and a var_iab+e frequency oscillator. T~e· primary objective was t9 develope a ll.L~ified · 2 des.ign a~proach for. ~oth circ:ui ts. The sp.ecificat:ions which the intermediate· freq~ency amplifier was expected to meet were; (1) a povrer gain of 50 db; (2) a one megacycle flat re­ sponse using stagger_tuning. The oscillator was to be_varia­ bly tuned. and operate at a frequency of ten megacycles. Importance .Q.f the study. Band pass amplifiers are used in many electronic applications. In any communication network where radio frequencies are used as the carrier .of informat.ion it is· necessary .to have at the receiving portion of ·the sy­ stem ample means for the amplification of the incoming s;gnal. The int~rmediate.frequen<?Y amplifiers ~n radio ~eceivers, :for example, provide up to _90% of the ·required gain, therefore, . these amplifiers are a major part of most receiving systems. Oscillators find application in many t.ypes of systems includ­ ing radar, radio, and television as prominent examples. It might ·be· well to point out, at this ~ime, that many of· the concepts used i.n design of •. low frequency amplifiers are appli_qable to high, frequency circuit desi~. wi_th some re­ servation. In general, the design of high frequency circuits are more complex due to the nature of the ·transistor and circuit components. 3 C. THE.SCOPE OF THE IMVESTIGATION ·The investigati~n was divided-into two parts, a theoretical analysis of the circuits and an experimental verification of the design. Theoretical investigation.· The design of the amplifier circuit involved an investigation of the neutralization of transistors, coupling ·networks, bias stability, _input im­ pedance measurements,