DESIGNING TRANSISTOR I.F. AMPLIFIERS

Transcription

1 DESIGNING TRANSISTOR I.F. AMPLIFIERS

2 By the same author: TRANSISTOR BANDPASS AMPLIFIERS The theory of analysis and design of selective amplifiers as used in the I.F. parts of radio, television and radar receivers, is here dealt with, especially in relation to the application of transistors. Single-stage amplifiers as well as multi-stage amplifiers, with arbitrary types of interstage or terminating networks are treated in detail as regards stability, power gain, amplitude response curve and envelope delay curve; also neutralization of the transistor internal feedback and problems associated with spreads in transistor parameters.

3 DESIGNING TRANSISTOR I.F. AMPLIFIERS W. Th. H. HETTERSCHEID 1966 SPRINGER-VERLAG BERLIN HEIDELBERG GMBH

4 This book contains xiv pages and 138 illustrations and 96 pages two-coloured design charts, 3 folding-out tables. U.D.C. nr : Library of Congress Catalog Card Number: Additional material to this book can be downloaded from ISBN DOI / ISBN (ebook) Springer-V erlag Berlin Heidelberg 1966 Originally published by N. V. Philips' Gloeilampenfabrieken, Eindhoven, The Netherlands, in 1966 Softcover reprint ofthe hardcover lst edition 1966 AU rights reserved rej PHILIPS Trade marks of N.V. Philips' Gloeilampenfabrieken No representation or warranty is given that the matter treated in this book is free from patent rights; nothing herein should be interpreted as granting, by implication or otherwise, a licence under any patent rights.

5 PREFACE In most cases the design of I.F. amplifiers for radio, television and radar receivers involves a large amount of computational effort. This is due to the numerous requirements imposed on such an amplifier which, in most cases, are contradictory. As a consequence, a compromise must usually be found which will result in an optimum performance of the amplifier with regard to the most important specification points. The above comments are applicable to all typts of I.F. amplifier, irrespective of whether they are equipped with electron tubes or transistors. The design of transistor I.F. amplifiers, however, imposes even more problems than that of the tube counterpart. This is due to the internal feedback of the tr~nsistors, which is not negligibly small. A transistor I. F. amplifier can, therefore, not be treated on a stage-by-stage basis as in the case of amplifiers equipped with modern penthode tubes, operating at a not too high frequency. The stage-by-stage design of a transistor I.F. amplifier is not possible because the internal feedback of the transistor in each stage affects the performance of all the other stages. This implies that an I.F. amplifier equipped with transistors must be treated as a whole. A new parameter is therefore added to the variety of parameters which already exists with tube equipped amplifiers: this new parameter being the amount of feedback present in each stage. In this book, a method is presented which facilitates that the design of transistor I.F. amplifiers can be carried out with great ease and accuracy. The key of this design method is formed by a large number of computed "design charts" which are used in connection with a step-by-step design procedure. These design charts contain amplitude response, envelope delay and gain characteristics, taking into account a certain set of parameters. One of these parameters is related to the amount of feedback of the transistors in the various amplifier stages. The step-by-step method of design leads to the choice of a particular set of design charts. Consultations of this set enables an accurate determination of the performance of the amplifier to be made. The design charts present moreover the information necessary for constructing the bandpass filters used as interstage networks. The subject-matter contained in this book is based on work carried out in the Philips Semiconductor Application Laboratory at Nijmegen, The Netherlands.

6 VI PREFACE The computed design charts are based on the analytical approach to amplifier design presented in the author's book "Transistor Bandpass Amplifiers". The author wishes to express his gratitude towards his colleagues for the many discussions and the helpful suggestions. In this respect he especially wishes to mention Mr. E. J. Hoefgeest and Mr. A. H. J. Nieveen van Dijkum. For correcting the manuscript the author is indebted to Mr. W. H. Cazaly, Ilford, England. March, 1966 The Author

7 CONTENTS Chapter 1 INTRODUCTION Chapter 2 THE DESIGN SPECIFICATION OF I.F. AMPLIFIERS Gain Gain Specifications of an I.F. Amplifier for a Television Receiver Gain Specification of an I.F. Amplifier for a Radio Receiver P.M. Receivers A.M. Receivers Amplitude Response Characteristic Radio Receivers Television Receivers Envelope Delay Characteristic 11 Chapter 3 SPREADS, TOLERANCES AND VARIATIONS IN I.F. AMPLIFIERS Definition of Various Groups of Deviations from Nominal Conditions Spreads Tolerances Variations Combination of Deviations from Nominal Conditions of Various Devices in Designing I.F. Amplifiers Method of Combining Various Deviations Spreads. Tolerances and Variations Encountered in I.F. Amplifier Design Chapter 4 TRANSISTOR PARAMETERS Admittance Parameters Transistor Parameter Nomenclature Dependence of Transistor Admittance Parameters on Operational Conditions Dependence of Transistor Admittance Parameters on Frequency Dependence of Input Admittance on Frequency 21

8 VIII CONTENTS Dependence of Reverse Transfer Admittance on Frequency Dependence of Forward Transfer Admittance on Frequency Dependence of Output Admittance on Frequency Dependence of Transistor Admittance Parameters on Voltage and Current Dependence of Input Admittance on Voltage and Current Dependence of Reverse Transfer Admittance on Voltage and Current Dependence of Forward Transfer Admittance on Voltage and Current Dependence of Output Admittance on Voltage and Current Dependence of Admittance Parameters on Temperature Dependence of Derived Transistor Quantities on Frequency, Voltage, Current and Temperature Spreads in Transistor Admittance Parameters. 47 Chapter 5 SURVEY OF I.F. AMPLIFIER DESIGN THEORY Stability Single-Stage Amplifier with Two Single-Tuned Bandpass Filters Multi-Stage Amplifier with Single-Tuned Bandpass Filters Single-Stage Amplifier with Two Double-Tuned Bandpass Filters Multi-Stage Amplifiers with Double-Tuned Bandpass Filters Basic Boundary of Stability Alignment Amplification Response Curve Resume 60 Chapter 6 NEUTRALIZATION. 61 Chapter 7 AUTOMATIC GAIN CONTROL OF TRANSISTOR I.F. AMPLIFIERS Reverse Gain Control. 65

9 CONTENTS IX Forward Gain Control Comparison of Signal Handling Capability of Reverse and Foreward Gain Control Effects of Input and Output Admittance Variations on the Response Curve Chapter PRACTICAL DESIGN METHOD FOR I.F. AMPLI- FIERS 72 Transistor Parameters Required for the Design. 72 The Regeneration Coefficient. 73 Limit Imposed on the Regeneration Coefficient by the Stability Requirement Amplifier without Neutralization Amplifier with Neutralization 74 Limit imposed on the Regeneration Coefficient by the R~oo~~~ ~ Amplifiers with Double-Tuned Bandpass Filters Spreads in g Spreads in gu Combined Effect of Spreads in g22 and ru Spreads in C22 and Cu Amplifiers with Single-Tuned Bandpass Filters Influences of Spreads in gu and g Effects of Spreads in Cu and C Summary of Remarks on the Regeneration Coefficient 81 The value of q2. 81 The Gain The Transducer Gain of the Complete Amplifier The Power Gain per Stage of the Amplifier The Voltage Gain per Stage of the Amplifier 94 Chapter EXAMPLES OF AMPLIFIER DESIGN. 98 An I.F. Amplifier for an A.M. Radio Receiver Regeneration Coefficient Determined by Stability Regeneration Coefficient Determined by Response Curve Requirements Definite Choice of the Regeneration Coefficient 100

10 X CONTENTS Design of the Double-Tuned Bandpass Filters The 3 db Bandwidth Adjacent Channel Selectivity Transimpedance Complete Circuit Diagram An I.F. Amplifier for F.M. Receivers with Double- Tuned Bandpass Filters General Design Considerations Regeneration Coefficient Determined by Stability Regeneration Coefficient Determined by Response Curve Requirements Design of the Double-Tuned Bandpass Filters The 3 db Bandwidth The Adjacent Channel Selectivity The Envelope Delay Gain Transducer Gain Gain per Stage Complete Circuit Diagram A Combined I.F. Amplifier for an A.M./F.M. receiver General Design Considerations of the Combined I.F. Amplifiers I.F. Amplifier for F.M Determination of Regeneration Coefficient Design of the Double-Tuned Bandpass Filters Gain and Frequency Response I.F. Amplifier for A.M Effects of the Emitter-Decoupling Capacitor Design for Stability Gain and Frequency Response Complete Circuit Diagram A Selective Amplifier for 35 Mc/s Regeneration Coefficient The Output Stage of the Amplifier Collector Circuit Base Circuit Transducer Gain of the Complete Amplifier 124

11 CONTENTS XI Power Gain of Stage Power Gain of Stage Power Gain of the Input Stage Amplitude Response Curve Dimensioning of the Tuned Circuits Circuit Circuit Circuits 3, 5 and Circuits 4 and Parasitic Effects Due to Capacitive Taps Complete Circuit Diagram 129 Chapter 10 EXAMPLE OF AMPLIFIER DESIGN TAKING INTO ACCOUNT DEVIATIONS FROM NOMINAL CONDITIONS General Choice of Transistor Biasing Points Design for Nominal Conditions Neutralization Determination of Bandpass Filter Parameters The Biasing Networks of the Various Transistors The Output Stage The Output Circuit The Input Circuit Stability The Second Stage The Damping Ratios Stability The Input Stage of the Amplifier with Reverse 138 A.G.C The Damping Ratios Stability The Input Stage of the Amplifier with Forward A.G.C The Damping Ratios Stability The Input Double-Tuned Bandpass Filter The Gain of the Amplifier The Output Stage The Second Stage 141

12 XII CONTENTS The Input Stage of the Amplifier with Reverse A.G.C The Input Stage of the Amplifier with Forward A.G.C The Input Double-Tuned Bandpass Filter The Gain of the Complete Reverse A.G.C. Amplifier The Gain of the Complete Forward A.G.C. Amplifier Complete Circuit Diagram Measurements The Reverse A.G.C. Amplifier The Amplitude Response Curve The Gain Dependence of Gain on Ambient Temperature Dependence of Gain on the Supply Voltage Linearity of the Amplifier Further Measurements The Forward A.G.C. Amplifier The Amplitude Response Curve The Gain Dependence of Gain on Ambient Temperature Dependence of Gain on Supply Voltage Linearity of the Amplifier Further Measurements Chapter 11 DESIGN EXAMPLES OF INCORPORATING SPREADS- THE CHOICE OF AN A. G. C.-SYSTEM FOR AN I.F. AMPLIFIER OF A TELEVISION RECEIVER The Various Signal Levels in I.F. Amplifier and Tuner The Permissible Signal Levels Spreads, Tolerances and Operational Variations Data of the I. F. Amplifier and the Tuner The Tuner Evaluation of Spread Factors

13 CONTENTS XIII Chapter The Transistor High-Frequency Properties The Second and Third Stages of the I. F. Amplifier The Input Stage of the I.F. Amplifier The Tuner The Detector Circuit The Dependence of Gain on Emitter Current The D. C. Properties of the Transistors Evaluation of Resistance Tolerances The Second and Third Stages of the I.F. Amplifier The Input Stage of the I.F. Amplifier The Tuner The Reference Levels of the A.G.C. Circuit Evaluation of Operational Variation The Contrast Control The Variations of Supply Voltage The I.F. Amplifiers The Tuner The Reference Levels of the A.G.C. Circuits The Variations in Ambient Temperature Combination of the Various Spreads, Tolerances and Operational Variations Spreads in Gain of the I. F. Amplifiers The Output Voltage of the Video Detector The Possible A. G. C. Range of the I.F. Amplifier The Overall Gain of Tuner and I.F. Amplifier Spreads in Overall Gain of Tuner and I. F. Amplifier Possible Delay of A.G.C. Cross-Over Point TheMixerStage The R.F. Stage The Choice of the Nominal Cross-Over Point 191 THE EFFECTS OF SPREADS IN TRANSISTOR ADMITTANCE PARAMETERS Amplifier Determinants with Spreads in Transistor Parameters Input-Damping Spread Factor Output-Damping Spread Factor

14 XIV CONTENTS Input-Tap Spread Factor Transistor Regeneration Coefficients The Coefficient of Coupling of the Double-Tuned Bandpass Filters The Normalized Admittances of the Tuned Circuits Survey of Terms of the Interchangeability Determinant Results of an Interchangeability Analysis. 200 Chapter 13 EXAMPLE OF CALCULATING THE GAIN PER FORMANCE OF AN I.F. AMPLIFIER FOR A TELEVISION RECEIVER Description of the Amplifier Gain Calculation Performance Measurements 212 Chapter 14 STEP-BY-STEP METHOD OF DESIGNING I.F. AMPLIFIERS Chapter 15 DESIGN CHARTS Choice of Tuning method Survey of Design Charts Single-stage amplifier with two-double tuned bandpass filters Two-stage amplifier with three double-tuned bandpass filters Three-stage amplifier with four single-tuned bandpass filters Four-stage amplifier with five single-tuned bandpass filters Three-Stage amplifier with four double-tuned bandpass filters Four-stage amplifier with five double-tuned bandpass filters Three-stage amplifier with three double-tuned and one single-tuned bandpass filters Four-stage amplifier with four double-tuned and one single-tuned bandpass filters