Week 12: 16-03-2020: Electronics

EE3C11 2020 Electronics

**Zoom Web Lectures **

Please study the topics listed in the presentations section below.

color coded resistors

Operational Amplifiers: Application, types and modeling techniques

Types of operational amplifiers

The operational amplifier was invented as a controller for analog computers. The “standard” operational amplifier has a floating (differential) voltage input and a grounded voltage output. Nowadays, different types of operational amplifiers exists.

Presentation

The presentation “OpAmps: types” briefly summarizes the historical development of operational amplifiers and lists the properties of the different types.

Video

Opamp Types (8:04)

Study

Chapter 8.1

Modeling of operational amplifiers

Manufacturers of operational amplifiers usually provide macro-models for SPICE simulation. Such models, however, do not provide design information.

Presentation

The presentation “Operational Amplifiers: modeling” presents techniques for modeling of specific behavioral apsects, for both SPICE simulators and for SLiCAP.

Videos

  1. Modeling of the behavior of operational amplifiers (10:37)
  2. Modeling of the small-signal dynamic behavior of oiperational amplifiers (5:17)
  3. (LT)spice nullor model (3:12)
  4. A programmable noise source for (LT)spice (3:47)
  5. Opamp model derived from datasheet (21:54)

Study

Chapter 8.3

Feedback amplifiers with standard operational amplifiers as controllers

Operational amplifiers are intended to be used as controllers in negative feedback amplifiers. Standard operational (voltage) amplifiers use both supply terminals as return path of the output port. This complicates the implementation of output current sensing.

Presentation

The presentation “Feedback configurations with operational amplifiers” illustrates this and presents alternative current sensing techniques.

Video

Feedback amplifier configurations with operational amplifiers (6:37)

Study

Chapter 8.4.1

Synthesis of multiple-controller feedback configurations

If a feedback amplifier comprises multiple controllers, alternative configurations that all have the same ideal gain can be found by pairing the nullators and norators differently.

Presentation

The presentation “Multiple-nullor circuit synthesis” demonstrates this technique for an active-feedback inverting voltage amplifier.

Study

Chapter 7.6.1

Introduction to biasing

Principle of amplification

Amplifiers can be constructed with devices of which the voltage-to-current transfer of the output port depend on their operating point.

Presentation

The presentation “Principle of amplification” shows the way in which a basic amplifier stage can be constructed with a “transresistance” device.

Study

Chapter 3

Introduction to amplifier biasing

Biasing is the application of a collection of techniques for fixing the electrical operating conditions of electronic devices, and deriving the required bias voltage and current sources from the power supply source(s).

Presentation

The presentation “Principle of biasing” shows the way in which bias sources fix the devices’ operating point, independent of the (passive) DC termination at the input port and the output port of the amplifier.

Study

Chapter 3

Biasing of operational amplifiers

Operational amplifiers are commonly used as controllers in feedback circuits. In order to operate, they should be biased properly.

Presentation

The presentation “Biasing of operational amplifiers” shows the biasing quantities that should establish the proper operating conditions for operational amplifiers.

Study

Chapter 8

Biasing example

Biasing example

Presentation

The presentation “Amplifier Biasing Example” presents a stepwise approach to the design of the biasing circuitry of an amplifier.

Study

Chapter 9.1, 9.2

Analysis and budgeting of biasing errors

Presentation

The presentation “Analysis and budgeting of biasing errors” presents simplified statistical techniques for budgeting of biasing errors.

Study

Chapter 9.3

Reduction of biasing errors

Presentation

The presentation “Reduction of biasing errors” discusses the application of error-reduction techniques for obtaining improved biasing accuracy and stability. An example of negative feedback biasing will be given.

Study

Chapter 9.4

SLiCAP source files Chapter 9

LTspice source files Chapter 8

Exercise 8.15 with SLiCAP

Discussion homework

  1. Selection of the feedback configuration for the active antenna, SLiCAP files: SLiCAP-EE3C11-3.zip.
  2. Evaluation of the noise figure with SLiCAP Exercise 4 from Exercises February 12
  3. Estimation of poles and zeros in passive networks with SLiCAP Exercise 1 from Exercises February 27

Homework

  1. Make SLiCAP .MODEL definitions that model the small-signal dynamic behavior of the following operational amplifiers:
    1. OPA211
    2. ADA4817
  2. Derive budgets for the equivalent-input voltage noise and the equivalent-input current noise sources of the controller of the antenna amplifier.
  3. Verify the noise behavior of the antenna amplifier that uses the ADA4817 as controller.
  4. Design a biasing solution for the active antenna in which the DC voltage at the output of the controller can be chosen independently from its common-mode input voltage range.
  5. Design an implementation of the above biasing concept that uses the ADA4817 as controller
  6. Evaluate biasing errors with SLiCAP. For this you use the SLiCAP-LTspice SLN_dcvar component and determine its parameters from the data sheet of the ADA4817.
  7. Does your biasing solution affect the noise behavior of the antenna amplifier?
  8. Does your biasing solution affect the bandwith of the antenna amplifier?
  9. Find design equations for the biasing components with SLiCAP.