Discussion of the exercises from previous days
Presentations
Note: scrolling through presentations
Always open presentations in a new tab: CRTL + click
Operational Amplifiers: Application, types and modeling techniques
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
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
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
Study
Chapter 8.3
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
Guidance with homework
The theory presented in day 4 will be applied in the design of the active antenna. Please use SLiCAP as documentation tool.
The ADA4817 is a JFET input low-noise operational amplifiers.
Make a small-signal dynamic model for SLiCAP, that models:
Please study the SLiCAP help for the built-in models of operational amplifiers
Model the noise behavior of this device; use a nullor with equivalent-input noise sources (LTspice symbol SLN_noise or SLO_noise), save this model for later use.
Model the DC biasing errors of this device; use a nullor with equivalent-input bias sources (LTspice symbol SLN_dcvar or SLO_dcvar), save this model for later use.
Give biasing design considerations for the operational amplifier to be used in the antenna amplifier and design a basic biasing solution for your preferred antenna amplifier concept. You may only use resistors for biasing!
