Equivalent Circuits - Resistors Resistor noise is dominated by thermal noise: Noiseless Resistor Noisy Resistor Noise Source.

Slides:

Advertisements

Similar presentations

Multi-stage Amplifiers

Advertisements

BJT Common Emitter Amplifier

MULTISTAGE AMPLIFIERS

Transistor Amplifiers

Transistors Fundamentals Common-Emitter Amplifier What transistors do

Frequency response I As the frequency of the processed signals increases, the effects of parasitic capacitance in (BJT/MOS) transistors start to manifest.

Using the Hybrid-  Model.  r bb and r o are omitted (insignificant)  R B represents parallel combination of R B1 and R B2  At high frequencies C.

By Squadron Leader Zahid Mir CS&IT Department, Superior University PHY-BE -19 Transistor as an Amplifier.

1 Chapter 6 Low-Noise Design Methodology. 2 Low-noise design from the system designer’s viewpoint is concerned with the following problem: Given a sensor.

Electrical Noise Wang C. Ng.

Common-Base vs. Common-Emitter

Low Noise Amplifier Design

1 Chapter 5 Sensors and Detectors A detector is typically the first stage of a communication system. Noise in this stage may have significant effects on.

Differential and Multistage Amplifiers

Cross-Over Distortion The non-zero “turn-on” voltage of a transistor causes cross-over distortion in a class B output stage. Approximate transistor response.

Practical Differential Amplifier Design We’ve discussed Large signal behaviour Small signal voltage gain Today: Input impedance Output impedance Coupling.

Noise in BJT The objective is to determine, and for a bipolar transistor. The hybrid- model that includes the noise sources is shown below Fig 5-3 The.

Radio Frequency Amplifiers In this section of the course: Why do common emitter amplifiers often have a disappointingly low upper cut-off frequency ? Where.

Department of EECS University of California, Berkeley EECS 105 Fall 2003, Lecture 18 Lecture 18: Bipolar Single Stage Amplifiers Prof. Niknejad.

Department of EECS University of California, Berkeley EECS 105 Fall 2003, Lecture 19 Lecture 19: Frequency Response Prof. Niknejad.

Dr. Nasim Zafar Electronics 1 - EEE 231 Fall Semester – 2012 COMSATS Institute of Information Technology Virtual campus Islamabad.

Power Electronics Lecture-7 Unijunction Transistor &

© 2012 Pearson Education. Upper Saddle River, NJ, All rights reserved. Electronic Devices, 9th edition Thomas L. Floyd Electronic Devices Ninth.

CHAPTER Noise 5.2 Transmission Media & EM Propagations.

1 Electronic Circuits COMMON EMITTER CIRCUITS. 2 Electronic Circuits AMPLIFIERS CAN BE CLASSIFIED AS EITHER: VOLTAGE AMPS POWER AMPS AMPLIFIERS CAN BE.

Microwave Amplifier Design

Transistors They are unidirectional current carrying devices with capability to control the current flowing through them The switch current can be controlled.

Chapter 5 BJT Circuits Dr.Debashis De Associate Professor West Bengal University of Technology.

Introduction to Transistors

1 Frequency response I As the frequency of the processed signals increases, the effects of parasitic capacitance in (BJT/MOS) transistors start to manifest.

Chapter 6. Bipolar Junction Transistors (BJTs). Bipolar Junction Transistor Three terminal device Voltage between two terminals to control current flow.

Chapter 2 Operational Amplifier Circuits

Noise characteristics Reference: [4] The signal-to-noise ratio is the measure for the extent to which a signal can be distinguished from the background.

Chapter 5: BJT AC Analysis

ECE 590 Microwave Transmission for Telecommunications Noise and Distortion in Microwave Systems March 18, 25, 2004.

Transistor Amplifiers

Chapter 6:BJT Amplifiers

Noise characteristics Reference: [4] The signal-to-noise ratio is the measure for the extent to which a signal can be distinguished from the background.

Advance Electronics Prof. Rajput Sandeep Assist. Prof., EC Dept. HCET,Siddhpur.

ECE 352 Electronics II Winter 2003 Ch. 8 Feedback 1 Feedback *What is feedback?Taking a portion of the signal arriving at the load and feeding it back.

Electronic Devices and Circuit Theory

Electronics Principles & Applications Fifth Edition Chapter 6 Introduction to Small-Signal Amplifiers ©1999 Glencoe/McGraw-Hill Charles A. Schuler.

© 2013 The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill 6-1 Electronics Principles & Applications Eighth Edition Chapter 6 Introduction.

EMT 112/4 ANALOGUE ELECTRONICS 1 Power Amplifiers Syllabus

ECE 352 Electronics II Winter 2003 Ch. 8 Feedback 1 *Feedback circuit does not load down the basic amplifier A, i.e. doesn’t change its characteristics.

Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Noise Designation.

Transistor Circuit DC Bias Part 1 ENGI 242. February 2003ENGI 2422 DC Biasing Circuits Fixed-Bias Circuit Emitter-Stabilized Bias Circuit Collector-Emitter.

 Power and power-gains are two main considerations in the design of a microwave transistor amplifier. To derive power and power-gains using traveling.

HW #5 7.10, 7.21, 7.71, 7.88 Due Tuesday March 3, 2005.

Other Transistor Circuits

1 LECTURE 7. Contents 5.Sources of errors 5.1.Impedance matching Non-energetic matching Energetic matching Non-reflective matching To.

Chapter 4 Bipolar Junction Transistors

TELECOMMUNICATIONS Dr. Hugh Blanton ENTC 4307/ENTC 5307.

EEM3A – Analogue Electronics Dr. T. Collins

Noise characteristics Reference: [4] The signal-to-noise ratio is the measure for the extent to which a signal can be distinguished from the background.

CHAPTER 1 (cont…) Part 2.1  Noise. Objectives To differentiate the types of noise To calculate the thermal noise generated by a resistor To calculate.

Noise characteristics Reference: [4] The signal-to-noise ratio is the measure for the extent to which a signal can be distinguished from the background.

Transistor Amplifier Basics It is critical to understand the notation used for voltages and currents in the following discussion of transistor amplifiers.

Chapter 3 – Transistor Amplifiers – Part 2 Special Amplifiers 1.Difference Amplifier 2.Complementary Symmetry 3.Cascading.

TE4201-Communication Electronics 1 2. Noise and Frequency Spectrum  AM communications system AM communications systemAM communications system  Noise.

1 Noise Figure Improvement using a Front End Transformer Hooman 9/9/13.

SUB.TEACHER:- MR.PRAVIN BARAD NAME:-SAGAR KUMBHANI ( ) -VIKRAMSINH JADAV( ) -PARECHA TUSHAR( ) TOPIC:-LINEAR AMPLIFIER(BJT.

BJT Circuits Chapter 5 Dr.Debashis De Associate Professor

Feedback Xs Xi Xo + - Xf βf

Frequency response I As the frequency of the processed signals increases, the effects of parasitic capacitance in (BJT/MOS) transistors start to manifest.

MECH 373 Instrumentation and Measurements

Chapter 5: BJT AC Analysis

Transistor Characteristics

Frequency response I As the frequency of the processed signals increases, the effects of parasitic capacitance in (BJT/MOS) transistors start to manifest.

ECE 352 Electronics II Winter 2003 Ch. 8 Feedback 1 Feedback *What is feedback?Taking a portion of the signal arriving at the load and feeding it back.

Presentation transcript:

Equivalent Circuits - Resistors Resistor noise is dominated by thermal noise: Noiseless Resistor Noisy Resistor Noise Source

Networks of Resistors Noiseless Resistor Noise Source NB. When adding noise sources, the result is the root of the sum of squares. Noiseless Resistor Noise Source

Transistors Usually, only consider noise sources associated with the base-emitter junction. These will be magnified by the gain of the amplifier. inin enen

Base Spreading Resistance, r bb Base spreading resistance, r bb, is the small, real resistance between the base terminal (the wire) and the actual base region of the transistor. Typical values are 100  or less. It is small enough to ignore in most circuit analysis. It is, however, a source of thermal noise.

Noise voltage sources We know that : r e is not a real resistance so it doesn’t generate any thermal noise. i c, however, will be contaminated by shot noise, therefore generating a noise voltage across v be.

Noise Sources in Transistors Noise voltage, e n, consists of thermal noise from r bb and shot noise in the collector current generating a voltage across r e. Noise current, i n, is dominated at high frequencies by shot noise in the base current.

Noise in Real Transistors Both the voltage and current noise sources will also contain a degree of flicker noise. This may dominate at low frequencies but be insignificant at high frequency. It is device dependent. Usually, plots of e n and i n for varying collector current and frequency are given in data sheets.

Low Noise Amplifier Design Noise voltage resulting from e n and i n : Noise Figure of amplifier:

Noise Figure vs. Source Resistance Source Resistance [  ] Noise Figure [dB]

Minimum Noise Figure To minimise noise figure, must minimise the term:

Noise Figure vs. Collector Current Usually, the source resistance is fixed (e.g. transducer output impedance) Noise figure can then only be optimised by either: Scaling the impedance with a transformer Choosing an appropriate collector current

Noise Figure vs. Collector Current Example, r bb = 100 ,  = 250, R S = 600 

Optimising I C To minimise NF, with respect to I C, minimise:

Optimising I C (cont) Minimum when derivative w.r.t. I C = 0

Theoretical Example A low noise common-emitter amplifier is required using a transistor with r bb = 100  and  = 250. The source resistance, R S = 600 .

Practical Low Noise Design Approximate expression for noise current neglects flicker noise It is, therefore, only valid at higher frequencies where flicker noise is low. For lower frequency design, either incorporate flicker noise in the equations or, more commonly, use noise figure plots provided in data sheets

Noise Figure Contour Plots

Summary In most amplifier circuits, the major sources of electrical noise are the source resistance, biasing resistors and the transistor/op-amp used for the input stage. As the source resistance is usually fixed, the optimal output signal-to-noise ratio can be achieved by minimising the Noise Figure. With transistor amplifiers, NF can be minimised by optimising the collector current: Using the approximating equations Using noise figure plots from a data sheet