# Circuit Idea

This novel electronics wikibook is for creative students, teachers, inventors, technicians, hobbyists and anyone who is not satisfied by formal circuit explanations. It is intended for people who really want to grasp the basic concepts of electronics by relying on their human imagination, intuition and emotions rather than on pure logic and reasoning.
This book is part of a series on Electric Circuits:
Circuit Theory Circuit Idea Digital Circuits Practical Electronics Electronics Analogue Electronics Semiconductors Materials in Electronics
In this book, we treat electronic circuitry not only as science but also as art. Inventing novel electronic circuits is a result of human fantasy, imagination and enthusiasm. Fortunately, abstract electronic circuits are based on clear and simple ideas, which we derive from our human routines. In order to really understand how circuits operate, we have first to reveal the basic ideas on which they are based. We just need to know what problem electronic elements solve, why they are soldered together, what they actually do in the circuit, how they do it, and more. As human beings, we just want to "see the forest for the trees."
Great circuit ideas are "non-electrical"; they are not dependent on the specific implementation (tube, transistor, op-amp etc.). The purpose of this wikibook is to reveal great circuit ideas, real truth about circuits. It just answers a simple but reasonable question:
Circuit idea is composed of two main logically connected parts: in the first part (Creating a circuit methodology), we create universal methods for unearthing the ideas behind circuits; then, in the second part (Revealing circuit ideas), we use these methods to reveal the secrets of popular circuits. The second part is designed as a collection of exciting stories about odd circuits and the amazing electrical phenomena behind them.
Following a novel building approach, the book presents every new more complex circuit based on the previous simpler one. First, we derive the most elementary passive building blocks from the basic electric circuits of Ohm, Kirchhoff, Thevenin and Norton. Then, we use these "bricks" to build more complicated compound passive circuits. Further, adding active elements in accordance with suitable basic ideas, we build various transistor circuits. Finally, applying the powerful negative feedback principle in all its forms, we transform these circuits into almost ideal op-amp ones.
Circuit idea also contains stories about circuit paradoxes, contradictions, conflicts, and building schemes to induce creativity in readers. Historical "excursions" show circuit evolution through the years. Some of the most interesting circuit stories are created by students during their exercises in the laboratory; they represent famous experiments (like Ohm's law). Other stories are derived from teacher's lectures and exercises.

## Completed circuit stories

Philosophy behind the Book (relying on human intuition, imagination and fantasy) How to Contribute to This Book (motivate, inspire and induce creativity in readers) How to Create a Circuit Story for this Book (showing the circuit evolution by building and reinventing the circuit) Involving Students from Technical University of Sofia in Circuit Idea Wikibook (a teacher's story) Why Circuit Ideas are Hidden (why inventors, authors, lecturers, professionals and producers hide circuit ideas) How to Hide Circuit Ideas ("useful" tips for beginning "idea hiders" - humor:) How to Kill Circuit Ideas ("useful" tips for beginning "idea killers" - humor:) Why Formulas Cannot Explain Circuits (their place is at the end of circuit design after intuitive explanations - humor:) How to Understand Circuits (analyzing the circuit structure, exploring the circuit operation and revealing the circuit idea) How to Present Circuits (introducing the circuit idea, building the circuit configuration and demonstrating the circuit operation) How to Invent Circuits (introducing the problem, looking for an idea, applying the idea, experimenting with the circuit and generalizing the results) Try to Invent! (the reader is motivated to become an inventor) Where to Start (setting the problem and waiting for the solution) In the Realm of Chance (stimulating the emergence of new ideas through the use of chance) The Inventor's Tools (examining the set of tools used by the inventor when solving inventive problems) Expanding the Toolbox (considered more "tools" used by inventors in solving creative tasks) Crystallization of the Idea (examined the moment immediately after the emergence of the new idea) How to Derive Basic Circuit Principles (provides insight into the tools with which to derive general principles from specific electronic circuits) Reinventing Circuits (to show the circuit evolution) Building Circuits (to construct more complex circuits by simpler building blocks) Using Analogies to Understand Circuits (scrutinizing famous pneumatic, hydraulic, mechanic, thermal and other analogies) Using Cause and Effect Relationships (seeing, introducing and changing the causality in circuits) Combining and Varying Electrical Quantities (to invent various circuits) Circuit Principles (a collection of basic circuit ideas derived from the specific circuit solutions) How to Visualize Voltages in Circuits (by voltage bars with proportional height) How to Visualize Voltages inside Resistors (by a voltage diagram) How to Visualize Currents in Circuits (by current loops with proportional thickness) How to Visualize Operating Point (by superimposed IV curves) Introducing Sensomotor Activities (to "sense" circuits) Functional Viewpoint (to generalize circuit ideas) Various Points of View (to generalize the notion about circuits) Putting yourself in the place of the device under study (to "sense" it) In the world of simulations (meeting CircuitLab) NEW My CircuitLab bag of tricks (a set of various simulating techniques) NEW Talking with Gemini (how to collaborate with Gemini AI, a personal story) NEW How to Extract Ideas from Our Mind's Eye and Record Them (practical tips about idea recording techniques) NEW Passive Voltage-to-Current Converter (assuming voltage causes current) Passive Current-to-Voltage Converter (assuming current causes voltage) Deriving a Series Voltage Summer from Kirchhoff's Voltage Law (a dual story) Building a Parallel Voltage Summer (by using more elementary circuit building blocks) Walking along the Resistive Film ("inventing" various resistive circuits by reproducing the famous Ohm's experiment nowadays) How do We Create Sinusoidal Oscillations? (an incredible story about the philosophy of LC tank) How to Make the Simplest Transistor Current Source (a bare transistor with steady input voltage or current)
Voltage Compensation reveals the philosophy behind the op-amp inverting circuits with negative feedback Op-amp Inverting Voltage-to-Current Converter (compensating the external losses by an "antivoltage") Op-amp Inverting Current-to-Voltage Converter (compensating the internal losses by an "antivoltage") Presenting the Op-amp Inverting Current-to-Voltage Converter in a More Attractive Manner How to Simplify the Design of the Mixed Op-amp Voltage Summer (after Dieter Knollman's original design idea) Revealing the Truth about ECL Circuits (switching voltage and current sources in the emitter) How to Reverse Current Direction (revealing the truth about basic current mirror) How the Wilson current mirror equalizes the currents (the first viewpoint at the legendary circuit) How the Wilson current mirror keeps up a constant output current (the second viewpoint at the legendary circuit) Negative Resistance is based on an old Wikipedia revision Negative Impedance Converter reveals the idea behind the weird circuit How to make an element with true negative resistance? is based on an answer to an SE EE question Negative Differential Resistance demystifies the ubiquitious phenomenon Revealing the Mystery of Negative Impedance is a general story about the mystic phenomenon Investigating the Linear Mode of Negative Impedance Converters with Voltage Inversion Investigating the Linear Mode of Negative Impedance Converters with Current Inversion Investigating the Bistable Mode of Negative Impedance Converters with Current Inversion Deborah Chung's "Apparent Negative Resistance" considers the greatest misconception in the area of the negative resistance phenomena

## Uncompleted circuit stories

Why Creative Persons are Unhappy (why "normal" people treat creative persons badly) <talk> Reinventing a Full-Wave Bridge Rectifier (by exploiting the powerful bridge idea) <talk> <group 64a> How do We Compensate the Diode Forward Voltage Drop? (introducing the passive compensation idea) <talk> Can a "Diode" Current Mirror Exist? (trying to build a current mirror with a diode current-setting part) <talk> <group 66b> How do We Build the Simplest Transistor Amplifier? (common-emitter amplifying stage) <talk> <group 65a> How to Make the Simplest Transistor Amplifier Bipolar (the famous biasing idea presented as a voltage shifting) <talk> <group 66a> How to Make an Analog Transistor Behave as a Digital One (building a transistor switch) <talk> <group 68a> Building an Emitter Follower (in sequence non-electrical > electrical > transistor follower) <talk> <group 67a> Building a Transistor "Zener Diode" (making voltage-stable elements by applying a parallel negative feedback) <talk> <group 64b> Building a BJT Current Mirror (by applying a parallel negative feedback to the current-setting part) <talk> <group 67b> Building an Op-amp Follower (in sequence non-electrical > electrical <talk> <group 65a> <group 66a> <group 67a> Building a Parallel NFB Inverter (overcoming the common ground problem by a parallel voltage summer) <talk> <group 65a> How Does an Active Follower Behave when Disturbed? (negative feedback systems overcome disturbances) <talk> <group 64b> <group 66a> How Can an Attenuation Cause an Amplification? (non-inverting amplifier) <talk> <group 65a> <group 66a> <group 67a> Creating Odd Circuits "without Input" (putting various resistive sensors in the feedback loop) <group 65b> <group 68b> Formulating "Golden Rules" for Using Disturbances Put into the Feedback Loop <group 65b> <group 68b> What Is the Great Idea behind Virtual Ground Phenomenon? <talk> How to Make Perfect Components (an ideal diode, transistor, capacitor, "superconductor", etc.) <talk> <group 68b> How to Make a Perfect Op-amp RC-integrator (obtaining an infinite capacitance) How Do We Swap Circuit Inputs and Outputs? (revealing the philosophy of the phenomenon) <talk> How to Transmute an Emitter Follower into an NFB Current Source (reinventing the famous circuit) <talk> <group 68b> Revealing the Secrets of 741 Op-amp Input Stabilization System <talk> Misleading the Op-amp of a Negative Feedback Circuit (introducing the positive feedback phenomenon) <talk> <group 64a> Converting the Op-amp Non-Inverting Amplifier into an Op-amp Inverting Schmitt Trigger <talk> <group 68a> Endowing a Transistor Switch with Memory (shows how to make a flip-flop) <talk> <group 67b> How to Compensate Resistive Losses by a Parallel Connected Negative Resistor (reinventing the famous NIC) <talk> Reinventing the Famous Deboo Integrator (shows the evolution of a passive RC circuit into a perfect active one) <talk> Investigating the Bistable Mode of Negative Impedance Converters with Current Inversion
Demystifying gyrator circuits
Relaxation versus LC Oscillators (comparison between the two kinds of creating oscillations) <talk>
Ring oscillators: yet another way of creating oscillations Common Circuit Questions (a list of questions, for which we need answers to understand, improve and invent circuits) Op-amp Inverting RC Integrator reveals the secret of the legendary circuit

## Table of contents

(contains a total of 184 titles of circuit stories)
ORGANIZING THE BOOK
    Philosophy behind the Book (relying on human intuition, imagination and fantasy)
    How to Contribute to This Book (motivate, inspire and induce creativity in readers)
    How to Create a Circuit Story for this Book (showing the circuit evolution by building and reinventing the circuit)
    Involving Students from TU Sofia in Circuit Idea (a teacher's story):
       2008: Group 64a • Group 65a • Group 66a • Group 67a • Group 68a (carrying out laboratory exercises during every even week)
       2008: Group 64b • Group 65b • Group 66b • Group 67b • Group 68b (carrying out laboratory exercises during every odd week)
       2010: Group 57a (building step-by-step a LED zero indicator)
CREATING A CIRCUIT METHODOLOGY
Revealing Circuit Ideas
    Why Circuit Ideas are Hidden (why inventors, authors, lecturers, professionals and producers hide circuit ideas)
       How to Hide Circuit Ideas ("useful" tips for beginning "idea hiders":)
       How to Kill Circuit Ideas ("useful" tips for beginning "idea killers":)
       Why Formulas Cannot Explain Circuits (formulas hide circuit structure and causality)
    How to Understand Circuits (analyzing the circuit structure, exploring the circuit operation and revealing the circuit idea)
    How to Present Circuits (introducing the circuit idea, building the circuit configuration and demonstrating the circuit operation)
    How to Invent Circuits (introducing the problem, looking for an idea, applying the idea, experimenting with the circuit and generalizing the results)
       The Secret of Invention (a series of seven articles about how to invent)
          Try to invent! (the first article in which the reader is motivated to become an inventor)
          Where to Start (setting the problem and waiting for the solution)
          In the Realm of Chance (stimulating the emergence of new ideas through the use of chance)
          The Inventor's Tools (examining the set of tools used by the inventor when solving inventive problems)
          Expanding the Toolbox (considered more "tools" used by inventors in solving creative tasks)
          Crystallization of the Idea (examined the moment immediately after the emergence of the new idea)
    How to Derive Basic Circuit Principles (provides insight into the tools with which to derive general principles from specific electronic circuits)
Heuristic Tools
    Using Mental Techniques to Manipulate Circuits
       Reinventing Circuits (to show the circuit evolution)
       Building Circuits (to construct more complex circuits by simpler building blocks)
       Using Analogies to Understand Circuits (scrutinizing famous pneumatic, hydraulic, mechanic, thermal and other analogies)
       Using Cause and Effect Relationships (seeing, introducing and changing the causality in circuits)
       Combining and Varying Electrical Quantities (to invent various circuits)
       Introducing Sensorimotor Activities (to "feel" circuits)
       Functional Viewpoint (to generalize circuit ideas)
       Various Points of View (to generalize the notion about circuits)
       Putting yourself in the place of the device under study (to "feel" it)
    Visualizing Invisible Electric Attributes
       How to Visualize Voltages in Circuits (by voltage bars with proportional height)
       How to Visualize Voltages inside Resistors (by a voltage diagram)
       How to Visualize Currents in Circuits (by current loops with proportional thickness)
       How to Visualize Operating Point (by superimposed IV curves)
    Carrying Out Unusual Experiments
       Carrying Out Imaginary Experiments (on a whiteboard, mental, etc.)
       Carrying Out "Man-Controlled" Experiments (a man acting as a transistor, op-amp, etc.)
       Why Old-Fashioned Meters Are Better than VOM for Educational Purposes (needle versus digit)
       Slow the Process Speed to Observe the Circuit Phenomena (using an integrator instead op-amp)
       "Live" Analogies (a computer simulated analogy synchronized with a real circuit arrangement)
    Carrying Out Simulating Experiments
       In the world of simulations (meeting CircuitLab) NEW
       My CircuitLab bag of tricks (a set of various simulating techniques) NEW
    Collaborating with artificial intelligence
       Talking with Gemini (how to collaborate with Gemini AI, a personal story) NEW
Creative Thinking Techniques
    How to Induce Creativity (collection of creative thinking techniques)
       How to Extract Ideas from Our Mind's Eye and Record Them (practical tips about idea recording techniques) NEW
    How Famous Circuit Inventors were Thinking when Inventing
    Why Creative Persons are Unhappy (why "normal" people treat creative persons badly) <talk>
REVEALING CIRCUIT IDEAS
    Building the Simplest Electric Circuit (introducing the electrical phenomenon by non-electrical means)
Transforming Energy by Passive Circuits
    Making Resistors Convert
       Voltage Causes Current
          What is a Voltage Source? (unusual negative feedback viewpoint at the classical voltage source)
          Passive Voltage-to-Current Converter (extracted from the famous voltage-supplied Ohm's circuit)
          Passive Voltage-to-Current Converter (Circuit Fantasia story)
          Passive Resistance-to-Current Converter (varying resistance as an input variable)
          Passive Voltage-by-Current Divider (varying both voltage and resistance as input variables)
       Current Causes Voltage
          What is a Current Source? (unusual negative feedback viewpoint at the classical current source)
          Passive Current-to-Voltage Converter (using a current-supplied Ohm's circuit)
          Building Current-to-Voltage Summer (applying Kirchhoff's Current Law)
          Passive Resistance-to-Voltage Converter (varying resistance as an input variable)
          Passive Current-by-Resistance Multiplier (varying both current and resistance as input variables)
       Voltage Causes Voltage
          Building a Voltage Divider (using V-to-I and I-to-V converter)
          Walking along the Resistive Film ("inventing" various resistive circuits by reproducing the famous Ohm's experiment)
             Discerning Typical Voltage Divider Applications (hair dryer, etc.)
          Building a Wheatstone Bridge (assembling the circuit by two voltage dividers)
          Deriving a Series Voltage Summer from Kirchhoff's Voltage Law
          Building a Parallel Voltage Summer (using V-to-I converters, an I-summer and an I-to-V converter)
             Presenting the Circuit by a First Class Lever Analogy (Give me the place to stand, and I shall move the earth)
             Exploring the Circuit by a Voltage Diagram ("inventing" the circuit by reproducing the famous Ohm's experiment)
             Exploring the Circuit by Superimposed IV Curves (introducing an operating point concept)
             Considering a Multiple Input Voltage Summer (mechanical analogies, calculating considerations)
    Endowing Circuits with Feeling of Time
       Accumulating Potential Energy into a Capacitor
          How Does a Capacitor Behave? (an intuitive explanation)
          Does the Current Flow through a Capacitor? (or, "Can a man pass through a wall"?:)
          Does the current flow through a capacitor, and if so, why? (ResearchGate question)
          Making a Capacitor Integrate (building a resistive-capacitive integrator)
          Deadening Voltage Variations by a Capacitor (How does a bypassing capacitor act?)
          Is a Capacitor a Voltage Source? (comparison with a "real" voltage source)
          Making a Capacitor Differentiate (building an "incorrect" capacitive and a "correct" capacitive-resistive differentiator)
          Shifting Voltage Variations by Capacitors (How does coupling capacitor act?)
          How Do We Obtain a Negative Voltage by a Positive Voltage Source? (building a split supply giving +12V and -12V in a car)
          How Does a Capacitor "Resist" AC Voltage? (What is a capacitive reactance?)
          Why the Current through a Capacitor Leads the Voltage across It by 90°? (an intuitive explanation)
          Why There Is a Varying Phase Shift between the Voltages in an RC circuit? (an intuitive explanation)
       Accumulating Kinetic Energy into an Inductor
          How Does an Inductor Behave? (an intuitive explanation)
          Making an Inductor Integrate (building an inductive-resistive integrator)
          Deadening Current Variations by an Inductor
          Is an Inductor a Current Source? (comparison with a "real" current source)
          Making an Inductor Differentiate (building an "incorrect" inductive and "correct" resistive-inductive differentiator)
          How Do We Obtain a Higher Voltage by Using a Self-induced EMF in a Coil (building a simple DC-DC converter)
          How Does an Inductor "Resist" AC Current? (What is an inductive reactance?)
          Why the Voltage across an Inductor Leads the Current through It by 90°? (an intuitive explanation)
          Why There Is a Varying Phase Shift between the Voltages in an RL circuit? (an intuitive explanation)
       Interchanging Energy between Accumulating Elements
          Transferring Energy between Homogeneous Accumulating Elements
             Discharging a Capacitor through a Capacitor (a conflict between "incorrect" connected voltage sources)
             Discharging an Inductor through an Inductor (a conflict between "incorrect" connected current sources)
          Interchanging Energy between Heterogeneous Accumulating Elements
             How do We Create Sinusoidal Oscillations? (creating a philosophy of the phenomenon) <talk>
             Building an LC tank (implementing the philosophy into an electrical circuit)
          Interacting with LC tank
             Connecting a Current Source in Parallel (an intuitive explanation of parallel resonance phenomenon)
             Connecting a Voltage Source in Series (an intuitive explanation of series resonance phenomenon) <talk>
       Making the Resistor Time-dependent
          What a Memristor Is (revealing the secret of memristor)
    Dynamizing Static Circuits
       Diode Acting as a Switching Element
          Reinventing a Full-Wave Bridge Rectifier (by exploiting the powerful bridge idea) <talk> <group 64a>
          "Inventing" a Series Diode Limiter (by connecting an ideal input voltage source in parallel to a real reference one)
          "Inventing" a Shunt Diode Limiter (by connecting an ideal reference voltage source in parallel to a real input one)
          Revealing the secret of diode AND logic gate <talk>
          Diode "OR" Circuits (blocking diodes, a reverse-polarity protector)
       Using a Diode as a Voltage-Stable Element
          What Does a (Zener) Diode Do in a Voltage Stabilizer? (giving an intuitive notion of a voltage-stable element)
          What Does a Diode Do in a Voltage Shifter? (diode biasing circuits)
          What Happens if We Connect in Parallel Two Different LEDs? (how do two constant-voltage element interact?)
          How do We Compensate the Diode Forward Voltage Drop? (introducing the passive compensation idea) <talk>
          Reinventing a Bipolar Diode Switch (similar to a bridge rectifier)
       Diode Acting as a Functional Element
          Logarithmic Diode Converter (a diode acting as a non-linear current-to-voltage converter)
          Antilogarithmic Diode Converter (a diode acting as a non-linear voltage-to-current converter)
       Current-Stable Circuits
          How to Make the Simplest Transistor Current Source (a bare transistor with steady input voltage) <talk> <group 65b>
          Can a "Diode" Current Mirror Exist? (trying to build a current mirror with a diode current-setting part) <talk> <group 66b>
Controlling Energy by Active Circuits
    Revealing the Secret of Amplification (there is no amplification; there is only regulation)
    How do We Build the Simplest Transistor Amplifier? (common-emitter amplifying stage) <talk> <group 65a>
    Reinventing the Common-Source Amplifier (NMOS common-source amplifier stage)
    How to Make the Simplest Transistor Amplifier Bipolar (the famous biasing idea presented as a voltage shifting) <talk> <group 66a>
    How to Make an Analog Transistor Behave as a Digital One (building a transistor switch) <talk> <group 68a>
Endowing Active Circuits with Negative Feedback
    Introducing the Active Copying Phenomenon (extracting the negative feedback great idea from human routine)
       Applying a Series Negative Feedback (using a series voltage summer as a subtractor)
          Building an Emitter Follower (in sequence non-electrical > electrical > transistor follower) <talk> <group 67a>
          Building an Op-amp Follower (in sequence non-electrical > electrical <talk> <group 65a> <group 66a> <group 67a>
       Applying a Parallel Negative Feedback (using a parallel voltage summer as a subtractor)
          Building a Parallel NFB Inverter (overcoming the common ground problem by a parallel voltage summer) <talk> <group 65a>
          Building a Transistor "Zener Diode" (by applying a parallel negative feedback) <talk> <group 64b>
          Building a BJT Current Mirror (by applying a parallel negative feedback to the current-setting part) <talk> <group 67b>
    Investigating NFB Circuits under Disturbances
       How Does an Active Follower Behave when Disturbed? (negative feedback systems overcome disturbances) <talk> <group 64b>
    Gaining an Amplification by an Attenuation
       How Can an Attenuation Cause an Amplification? (non-inverting amplifier) <talk> <group 65a> <group 66a> <group 67a>
       Can we make an attenuator act as an amplifier? (ResearchGate question)
       Converting an Op-amp Inverter into an Op-amp Inverting Amplifier (overcomming the common ground problem)
    Using a Varying Disturbance as an Input Quantity
       Creating Odd Circuits "without Input" (putting various resistive sensors in the feedback loop) <group 65b> <group 68b>
       Formulating "Golden Rules" for Using Disturbances Put into the Feedback Loop <group 65b> <group 68b>
    Making Negative Feedback Circuits Interact
       Causing Conflicts Between Voltage Sources
          An Unusual Look at the Classic Common-Base Amplifier (presenting the circuit as an output-disturbed emitter follower)
          Creating Emitter-Coupled Circuits (by provoking a conflict between two voltage sources)
          Revealing the Truth about ECL Circuits <talk>
          Reinventing the Transistor Differential Amplifier (by provoking a dramatic conflict between two input voltage sources)
          Revealing the Conflict in the Op-amp Instrumentation amplifier (two voltage followers fight each other)
       Causing Conflicts Between Current Sources
          Obtaining a High Gain by a Current Conflict (reinventing the amplifier with dynamic load)
          Obtaining an Extremely High Gain by a Dramatic Current Conflict (reinventing the amplifier with current mirror)
       Making Circuits Help Mutually
          A Current Source Helps a Voltage One (revealing the secret of amplifiers with emitter current source)
          A Voltage Source Helps a Current One (disclosing the secret of mystic cascode circuits)
       Transforming Imperfect Passive Circuits into Better Transistor Ones
          What is the idea of the Miller theorem? (Wikipedia page)
          Reinventing the Famous Miller Integrator (increasing capacitance)
             Revealing the Secret of a Staircase Light Timer (showing a typical Transistor Miller Integrator Application)
       Transforming Imperfect Passive Circuits into Perfect Op-amp Ones
          What Is the Great Idea behind Virtual Ground Phenomenon? <talk>
          How Do We Transform Imperfect Passive Circuits into Perfect Op-amp Inverting Circuits? (a philosophy)
          How to Transmute the Passive Voltage-to-Current Converter into an Op-amp Inverting One (making zero resistance)
          ..............................................Ammeter......................................................................... (...........zero resistance)
          How to Transmute the Passive Current-to-Voltage Converter into an Op-amp Inverting One (making a zero resistance)
             Presenting the Op-amp Inverting Current-to-Voltage Converter in a More Attractive Manner
          ..............................................Voltage Divider into .............. an Op-amp Inverting Amplifier (...........zero resistance)
          ..............................................Parallel Voltage Summer.................................................. (...........zero resistance)
          How to Simplify the Design of the Mixed Op-amp Voltage Summer (after an EDN's article)
          How to Make a Perfect Op-amp RC-integrator (obtaining an infinite capacitance) <talk> <group 67a>
          ..............................................CR-differentiator............................................................... (...........zero resistance)
          ..............................................Logarithmic Converter....................................................... (...........ideal diode)
          How to Make Perfect Components (an ideal diode, transistor, capacitor, "superconductor", etc.) <talk> <group 68b>
    Reversing Circuit Causalities by Applying a Negative Feedback
       How Do We Swap Circuit Inputs and Outputs? (revealing the philosophy of the phenomenon) <talk>
       How to Convert the Passive Voltage Divider into an Op-amp Non-inverting Amplifier (another viewpoint at non-inverting amplifier)
       How to Transmute an Emitter Follower into an NFB Current Source (reinventing the famous circuit) <talk> <group 68b>
       How to Transmute a Current-to-Voltage Converter into an Op-amp Voltage-to-Current Converter (NFB op-amp current source)
       How to Reverse Current Direction (revealing the truth about basic current mirror)
       How the Wilson current mirror equalizes the currents (the first viewpoint at the legendary circuit)
       How the Wilson current mirror keeps up a constant output current (the second viewpoint at the legendary circuit)
    Subtracting Input Quantities
       Op-amp Differential Amplifier (merging the inverting and non-inverting circuits)
          Presenting the Circuit by Lever Analogies (combining an one-input and a two-input second class lever analogy)
       Op-amp Fully Differential Amplifier (merging two inverting circuit)
          Understanding Integrated Fully Differential Amplifier (scrutinizing the internal circuit structure)
          Presenting the Basic FDA Circuit by Lever Analogies (combining two-input second class lever analogies)
Endowing Active Circuits with Positive Feedback
       Misleading the Op-amp of a Negative Feedback Circuit (introducing the positive feedback phenomenon) <talk> <group 64a>
    Endowing Circuits with Hysteresis
       How do We Create a Hysteresis? (revealing the philosophy of the great phenomenon)
       Reinventing Transistor Schmitt Trigger
          Revealing the Secret of an Electronic Toaster (showing a typical Schmitt Trigger Application)
       Converting a Transistor Schmitt Trigger into a Flip-Flop Circuit
       Endowing a Transistor Switch with Memory (shows how to make a flip-flop) <talk> <group 67b>
       Converting the Op-amp Non-Inverting Amplifier into an Op-amp Inverting Schmitt Trigger <talk> <group 68a>
       Converting an Op-amp Inverting Amplifier into an Op-amp Non-Inverting Schmitt Trigger
       Creating Relaxation Oscillations
          How to Make the Voltage across a Capacitor Wiggle (creating a philosophy by comparing with the LC phenomenon)
          Building Simple Relaxation Oscillators (by using neon lamps and other devices having hysteresis)
          Building an Op-amp Functional Oscillator (by using an integrator and an op-amp comparator with hysteresis)
          Building the Famous Timer 555
    Sustaining Sinusoidal Oscillations in Electronic Circuits
       How to Help an LC Tank (revealing the general idea behind LC electronic oscillators) <talk>
          Armstrong's Idea
          Hartley's Idea
          Colpitts's Idea
       How to Make an RC Circuit Produce a Sinusoidal Oscillation (revealing the general idea behind RC electronic oscillators)
       Comparison between Oscillators (comparison between relaxation, LC and RC oscillators) <talk>
    Sustaining square-wave oscillations in electronic circuits
       Ring oscillators: yet another way of creating oscillations
    Putting in Practice the Munchhausen's Bootstrapping Idea
       How do We Create an Infinite Input Resistance? (revealing the idea behind a bootstrapped amplifier)
       How do We Create an Infinite Output Resistance? (revealing the idea behind a bootstrapped current source)
       Reinventing the Improved Howland Current Source (by using the output bootstrapping idea)
    Making "Positive" Resistance Negative
       Negative Resistance is based on an old Wikipedia revision
       Negative Differential Resistance is based on an old Wikipedia revision
       Creating a circuit with negative differential resistance is based on an answer to an SE EE question NEW
       Revealing the Mystery of Negative Resistance (Impedance) is a general story about the mystic phenomenon
       How to make an element with true negative resistance? is based on an answer to an SE EE question NEW
       Negative Impedance Converter reveals the secret of the mystic 3-resistor circuit
       How do We Create Dynamic Resistance?
       How do We Make Decreased, Zero and Negative Resistance?
       How to Compensate Resistive Losses by a Series Connected Negative Resistor (reinventing the famous NIC)
       Investigating the Linear Mode of Negative Impedance Converters with Voltage Inversion
       Investigating the Linear Mode of Negative Impedance Converters with Current Inversion
       Investigating the Bistable Mode of Negative Impedance Converters with Current Inversion
       How do We Make Increased, Infinite and Negative Resistance?
       How to Compensate Resistive Losses by a Parallel Connected Negative Resistor (reinventing again the famous NIC) <talk>
       Reinventing the Famous Howland Current Source (a negative resistance "neutralizes" a positive one) <talk>
       Reinventing the Famous Deboo Integrator (comparison between Miller and Deboo integrator) <talk>
       Demystifying gyrator circuits
       Deborah Chung's "Apparent Negative Resistance (a story about the great scientific misconception in negative resistance area)
Revealing the Secret of Mixed (Analog & Digital) Circuits
    Making Digital Quantities Analog
       Revealing the Philosophy of the Digital-to-Analog Conversion (materializing an abstract digital code)
       Building a Simple Digital-to-Analog Convertor (based on a parallel voltage summer with binary-weghted input resistors)
       Building an R-2R Ladder DAC (based on an op-amp inverting current summer with an input R-2R ladder)
       Using a DAC as a Digital-to-Analog Convertor (applying a constant reference voltage and a varying input code)
       Using a DAC as a Digital-Controlled Amplifier (a varying "reference" voltage and a constant digital code)
       Using a DAC as a Digital-by-Analog Multiplier (a varying input voltage and a varying digital code)
    Making Analog Quantities Digital
       Revealing the Philosophy of the Analog-to-Digital Conversion (using a negative feedback viewpoint)
       Building an Analog-to-Digital Convertor (by a DAC and a comparator)
       Using an ADC as an Analog-to-Digital Convertor (applying a constant reference voltage and a varying input voltage)
       Using an ADC as an Analog-by-Analog Divider (a varying "reference" voltage and a varying input voltage)
       Using an ADC as a Digital Sample & Hold Circuit ("freezing" the DAC)
COLLECTIONS
    Circuit Principles (a collection of basic circuit ideas derived from the specific circuit solutions)
    Circuit Building Schemes (a short collection of circuit building "formulas")
    Circuit Paradoxes (odd, absurd and mystic circuit phenomena)
    Circuit Contradictions
    Common Circuit Questions (for which we need answers to understand, improve and invent circuits)
    Specific Circuit Questions about basic circuits
Resources
    Wikimedia Resources
    External web resources