ECE/EEE/INSTR F244 Micro Electronics Circuits

Transcription

1 BITS Pilani Dubai Campus ECE/EEE/INSTR F244 Micro Electronics Circuits Dr Jagadish Nayak

2 Introduction BITS Pilani Dubai Campus

3 Course outline Transistor Circuits for micro electronics leel Study BJT and MOSFET amplifier characteristics Multistage amplifiers Feedback amplifies Output stage amplifies Power amplifiers Op-Amps Frequency responses characteristics of all the aboe

4 Pre-requisites Construction and working principles of BJT, MOSFET Elementary circuit theory Concept of frequency Actie and passie elements Concepts of Voltage, current, and Power

5 Lecture Hour and Tutorial Entire Semester lecture and Tutorial plan is aailable There will be three lecture hours and one tutorial hour in a week. Attendance will be taken for both lecture and Tutorial hour Eery topics can be practically implemented by a software tool called as PSPICE. Students are supposed to learn this tool by themseles Introduction class on PSPICE is taken in the Tutorial class only All students must submit the assignment on PSPICE PSPICE software is aailable freely as Limited student ersion from the website

6 Introduction to Amplifiers What is an amplifier?? System which amplify a small quantity into large quantity In Electronics we are more interested on amplification of Electrical quantities such as oltage, current and Power. BJT and MOSFETs can be used as an amplifier. These components are the basic building blocks of the amplifier. Amplifier circuits are embedded in small package in many stages and aailable in micro leel. Design of this amplifier circuit in micro leel is in High demand in present scenario.

7 General Characteristics Signal Amplification Let us consider a Microphone (Transducer), Output of the microphone is raised to mv, which is called as signal amplification. The amplifier has to be linear.

8 General Characteristics Let output of the amplifier be 0 (t) for an input of i (t) at time instant t The input output relation is 0 (t)=a i (t) Where A is called as Gain of the amplifier.

9 Circuit Symbol

10 Voltage Gain Consider following amplifier Voltage gain A 0 I

11 Transfer characteristics

12 Power Gain, Voltage gain Power Gain( A p ) Load Input Power Power ( P ) L ( P ) I 0 I i i 0 I Current Gain( A i ) i i 0 I

13 Gains in Decibels Voltage gain in decibels =20 log A Current gain in decibels =20 log A i Power gain in decibels =10 log A p

14 Power Supplies for the amplifiers Amplifier need power supplies to operate. Typical amplifier requires two power supplies as shown below

15 Power Supplies for the amplifiers

16 Power Supplies for the amplifiers The net dc power deliered to the Load is P dc =V 1 I 1 +V 2 I 2 If the power dissipated in the amplifier is denoted by P diss The power balance equation for the amplifier is P dc +P I =P L +P diss Where P I =Power drawn from the signal source (normally small) And P L is Power deliered to the Load Amplifier efficiency P P L dc x100

17 Amplifier Saturation An amplifier transfer characteristic that is linear except for output saturation

18 Non-Linear transfer characteristics and Biasing Practical amplifier may exhibit non-linearity in its transfer characteristics.

19 Non-Linear transfer characteristics and Biasing The operating point is selected by the biasing of the transistor amplifier circuits. This is done as shown below. I ( t) V I ( t) i Where O ( t) V I O ( t) totalinstantanious input o ( t) Where O ( t) total ( t) A ( t) o i instantanious input A d d O I at Q

20 Non-Linear transfer characteristics and Biasing A is slope of the almost linear segment of the transfer cure. So for the linear amplification, there is a limitation, what is that The input signal must be kept sufficiently small so that input amplitude will not reach non-linear portion. This distortion is undesirable This approximation is called as small-signal approximation.