A System of Basic Circuit Pinciples

The Idea

In the mid-1990s, I had already managed to build my own "philosophy" of electronic circuits, and the idea arose in me to make a hierarchical classification of the universal principles on which specific circuits are built. My rationale for this was based on my observations that the seemingly large variety of electronic circuits and devices is actually based on a small number of clear and ingeniously simple fundamental ideas. The formulation of such universal circuit engineering principles, I thought, and their arrangement in a hierarchical system, would allow us not only to analyze in depth the operation of electronic circuits revealing their mutual relationship, but also to create, synthesize, pseudo-invent, and even truly invent new devices. In this endeavor, I was greatly influenced by Altshuller's 40 principles that he developed in the field of mechanical engineering.

Classification

Here I share my experience in systematizing circuit principles, "tricks" and effects in the field of analog circuitry. The classification consists of four main parts. In the first I have included universal principles of inventive creativity that can be found in all areas of analog circuitry. In the remaining three parts, I have revealed the principles for building passive analog devices, devices without negative feedback, and devices with negative feedback. I have illustrated the principles both with specific devices from the field of analog circuit engineering and with "non-electrical" examples from life.

General principles

Turning loss into gain

The "harmful" hysteresis becomes useful

Eliminating the influence of interference superimposed on the useful signal
Debouncing mechanical contacts
Getting memory

Converting a Schmitt trigger to an RS-latch
Converting a reed contact from a "button" to a "switch"

The "harmful" threshold voltage VF becomes useful

"Zener Diode" with low threshold voltage
Artificially raising the threshold voltage of an LED so that it can be "turned off" by another LED

The "harmful" temperature dependence of the threshold voltage VF u VBE becomes useful

Diodes and transistors acting as semiconductor temperature sensors

The "harmful" nonlinearity of the characteristic becomes useful

Obtaining logarithmic and anti-logarithmic function by semiconductor diode

Pre-deliberate deterioration with the idea of future improvement

Annihilating a harmful quantity with a useful "anti-quantity"

Passive destruction (in circuits without negative feedback)
Active destruction (in circuits with negative feedback)

Splitting the functions of a device into multiple functions and assigning them to different devices (only one of them is active at a given time)

Push-pull stage (emitter follower with bipolar output)
Bridge circuits

Principles for Building Passive Analog Devices with Resistors

Principles derived from Ohm's law

Principles applied to an electrical circuit driven by an ideal voltage source

Converting voltage to current

Building a current source using a voltage source
Building a voltmeter using an ammeter
Base resistor in a transistor switch (CB stage)
Integrating circuit
Logarithmic circuit

Converting resistance to current

Building an ohmmeter using an ammeter
Resistive sensors with current output

Dividing voltage by resistance

Multiplying digital-to-analog converter (R-2R ladder) with current output

Principles applied to an electrical circuit driven by an ideal current source

Converting current to voltage

Current-to-voltage converter

Building a voltage source using a current source
Building an ammeter using a voltmeter
Differentiating circuit

Converting resistance to voltage

Building an ohmmeter using a voltmeter
Resistive sensors with voltage output

Multiplication of current by resistance

Multiplying digital-to-analog converter (R-2R ladder) with voltage output

Principles derived from the equivalent circuits of real electrical sources

applied to an electrical circuit driven by a real voltage source (after Thevenin)

Converting voltage to voltage

Voltage divider

Converting resistance to voltage

Series regulation of electrical energy: transistor amplifier, series regulator
Resistive sensors with "voltage" output: thermo-, photo-, tenso-, etc. (linear output only within small limits)

Converting the ratio of resistances to voltages

Potentiometric resistive sensors with "voltage" output (linear output)
Potentiometric voltage regulation

Multiplying voltage by resistance ratio

Analog multiplier

applied to an electrical circuit driven by a real current source (after Norton)

Converting current to current
Current divider

Shunt (in ammeters)

Principles derived from Kirchhoff's laws

Principles derived from KCL

Parallel summing, subtracting and comparing currents

Parallel summing currents

Current summer
Circuits with parallel positive feedback

Parallel subtracting currents

Current subtractor

Parallel comparing currents

Current comparator
Circuits with parallel negative feedback

Parallel summing, subtracting and comparing voltages by intermediate converting to currents

Parallel summing voltages

Voltage summer
Converting an ADC with a unipolar positive input to a bipolar one
Circuits with parallel positive feedback

Parallel subtracting voltages

Voltage subtractor
Converting a DAC with a unipolar positive output to a bipolar one

Parallel comparing voltages

"Virtual ground" principle

Parallel voltage comparator (electrical "scale")

Principle of the "immovable virtual ground" (simultaneous opposite change of both input voltages)

Circuits with parallel negative feedback

Principle of the "movable virtual ground"

Principle of "scissors" (changing one voltage)
Principle of "guillotine" (simultaneous unidirectional change of both voltages)

Principles derived from KVL

Series summing, subtracting and comparing currents

Series summing voltages

Voltage summer
Circuits with series positive feedback

Series subtracting voltages

Voltage subtractor

Series comparing voltages

Voltage comparator
Circuits with series negative feedback

Principles for Building Passive Analog Devices with Reactive Elements

Passive voltage copying

Initial charging of the decoupling capacitors in RC-coupled AC amplifiers
"Sample & hold" circuit in sample mode

Dynamic "shifting" voltage variations ("coupling" a voltage to another voltage)

Decoupling capacitors in AC amplifiers (converting a bipolar to unipolar voltage and vice versa)
Circuits with artificial increasing resistance ("bootstrapping")
Positive feedback capacitor in a Hartley oscillator

Dynamic "hardening" of "soft" voltage

Filtering capacitor
Converting a real to an "ideal" voltage source

Potentiometer shunted by a capacitor
Average detector

"Fast charging - slow discharging"

Peak and amplitude rectifier
Increasing the speed by forcing the current (overcoming stray capacitances)

"Slow charge - fast discharge"

Relaxation oscillators
Photo flash
Impulse magnetization of permanent magnets
Charge dosing
Capacitive ADC

Reversing voltage polarity

Symmetrical multivibrator
Power supplies

Current forcing

Transistor switch with accelerating capacitor

Generating linearly changing voltage

Sweep circuits in CRT
ADC implemented by comparing the input voltage with a linearly varying voltage

Generating step changing voltage
Rising the voltage across a coil

DC-DC converter

Principles for Building Electronic Analog Devices without Negative Feedback

Principle of dynamic resistance

RV-type dynamic resistance

Diodes (ordinary, zener, LED, etc.)

RI-type dynamic resistance

Transistors

Negative resistance

Tunnel diode amplifier
Circuits with artificially created negative resistance

Regulating (generating, amplifying) voltage through a voltage divider composed of series-connected resistors

by changing the resistance of one resistor while keeping the resistance of the other constant (ohmic resistor)

"Floating" regulating element

"Common emitter" circuit with a positive supply and a PNP transistor

Grounded regulating element

"Common emitter" circuit with a positive supply and a NPN transistor

by changing the resistance of one resistor while the other resistor "helps" it in trying to change the output voltage (RI-type non-linear resistor)

where both elements are RI-type nonlinear resistors

Amplifier with dynamic load

by changing (simultaneously and oppositely) the resistance of both resistors (resistance redistribution)

Complementary (push-pull) stage

Where both elements are RI-type nonlinear resistors

Regulating current through a current divider composed of resistors connected in parallel

by changing the resistance of one resistor while keeping the resistance of the other constant (ohmic resistor)
by changing the resistance of one resistor while the other resistor "helps" it in trying to change the output voltage (RV-type nonlinear resistor)

where only one element is RV-type nonlinear resistor

Zener diode voltage stabilizer

where both elements are RV-type nonlinear resistors

"Turning off" LEDs with different threshold voltages

Zero voltage LED indicator

Switching zener diodes (the diode with the lower threshold voltage "turns off" the diode with the highest voltage)

by changing (simultaneously and oppositely) the resistance of both resistors (resistance redistribution)

Differential amplifier

Static "movement" of voltage changes

through a current source creating a constant voltage drop across a resistor

Output stages of operational amplifiers

through a nonlinear element with V-type IV curve

Compensating the base-emitter voltage VBE in the bias circuits in the output amplifier stages (class AB)

Passive compensation of harmful quantities by "anti-quantities"

Compensating vision defects (myopia, farsightedness, astigmatism) with glasses
Compensating the forward voltage drop VF in a diode rectifier (detector, limiter) by a reverse voltage created on a second diode
Compensating for nonlinear distortions in a push-pull stage, class AB
Compensating the influence of the input bias currents of an operational amplifier by inserting the same resistors in both inputs
Temperature compensation

in bias circuits of amplifier stages

through thermistors
through diodes

in circuits producing reference voltage

in constant current sources

Principles for building electronic analog devices with negative feedback

"Active copying" principle

"Active copying" with serial comparing

Emitter follower
Op-amp voltage follower

"Active copying" with parallel comparing

Op-amp voltage inverter

Principle of "disturbed active copying" (suppression of disturbances in a negative feedback system)

Suppressing additive disturbances

Eliminating the diode threshold voltage VF in a precision diode rectifier (detector, limiter)
Eliminating the transistor threshold voltage VBE in an emitter follower put in the op-amp negative feedback loop
Compensating the voltage drop along a long supply wire by a negative feedback voltage stabilizer (the idea of the three-wire connection)
Compensating the voltage drop across the op amp output resistance

Suppressing multiplicative disturbances

Compensating for attenuation in the Rout-RL divider of an op-amp voltage follower and voltage inverter

Principle of "intentional disturbed active copying" (intentional disturbing voltage follower with negative feedback)

Converting a follower system into an amplifier system by deliberate constant disturbing

Transistor amplifier stages

"Common-emitter stage with negative feedback ("emitter degeneration")
Phase splitter

Op-amp amplifiers with negative feedback

Inverting amplifier
Non-inverting amplifier

Deliberately varying disturbance of a follower system with negative feedback (the output signal becomes a function of the disturbance)

Multiplicative disturbance

Resistance-to-voltage converter (putting thermal, photo, etc. resistive sensors in the negative feedback network)

"R1-V"
"R2-V"
"P-V"

Digital-to-analog converter with R-2R ladder

Additive disturbance

Measuring the voltage VF of diodes and LEDs, batteries, etc.

Deliberately disturbing a follower system with negative feedback by "attacking" its output (there is a conflict; the system reacts to attempts to change its output signal)

"Attacking" a voltage source

Common-base stage
Emitter-coupled circuits

"Attacking" a current source

Transistor stage with dynamic load

Mutual disturbing follower systems connected by their outputs to each other (there is a conflict; systems react to attempts to change their output signals)

Conflict between two voltage sources

Differential amplifier (mutual disturbing of two follower systems)

Conflict between two current sources

Transistor stages with controlled dynamic load

Principle of mutual "helping" between various nfollower systems with negative feedback

voltage sources
current sources
voltage source and current source

Differential amplifier with a current source included in the transistor emitters at common-mode
Cascode circuits - a current source driving a voltage source through its output

Reversing cause-and-effect relationships in analog devices through the principle of active copying (swapping their input and output)

Reversed non-inverting voltage divider of the type 1/(1 +R1/R2) - we change the "output" voltage of the divider so that the voltage across the resistor R2 is equal to the input voltage
Reversed R2/R1 type inverting voltage divider - we change the "output" voltage across resistor R2 so that the voltage across resistor R1 is equal to the input voltage (we change the total voltage applied across the two series-connected resistors so that the voltage across resistor R1 to be equal to the input voltage)
Integrator > differentiator - we change the "output" voltage of an integrating circuit so that the voltage across the capacitor is equal to the input voltage
Differentiator > integrator - we change the "output" voltage of a differentiating circuit so that the voltage across the resistor is equal to the "input" voltage
Reversed frequency divider - we change the "output" frequency so that after division it is equal to the input (PLL circuits)

Principles of converting passive analog devices to active

Active copying with removing the original (removing of disturbance by anti-disturbance)

without using the copy (we only destroy the harmful disturbance, providing ideal conditions for the circuit to work)

Maintaining a constant current by destroying the harmful voltage drop across the "disturbing" element

Charging rechargeable battery
Driving LEDs, DC motors, electromagnets
"Ideal" ammeter and ohmmeter
Voltage/resistance divider

Maintaining a constant voltage by eliminating the harmful current leakage through the "disturbing" element

using the copy (we judge the degree of disturbance according to the "anti-disturbance")

"Ideal" current-to-voltage converter

"Ideal" ammeter made with a real voltmeter

An "ideal" resistance-to-voltage converter

"Ideal" ohmmeter made with a real voltmeter
"Ideal" resistive sensors with output voltage

"Ideal" current x resistance multiplier
"Ideal" parallel summer
"Ideal" integrator and differentiator
"Ideal" logarithmic and anti-logarithmic device
Measuring the diode forward voltage VF

Active copying without destroying the original

A current meter in a circuit supplied by an ideal current source
"Ideal" ohmmeter made with an ideal current source and a real voltmeter
Non-inverting resistor voltage adder
"Ideal" current integrator

Principles for inventing analog devices by simultaneous operation of the two op-amp inputs

Follower with controlled gain sigh (+1 or -1)
Op-amp differential amplifier

Principles for inventing analog devices by applying both negative and positive feedback

Current source with grounded load (Howland current pump)
Circuits with negative resistance

Artificial dynamic change of electrical circuit parameters

Dynamic increasing resistance by "active copying" (following negative feedback, bootsrapping)

Increasing the input resistance of systems with series negative feedback (voltage follower)
Eliminating the shunting effect of the biasing divider in a transistor amplifier
Artificial increasing Rc in output transistor stages
Eliminate the influence of on-board leakage acting between the op-amp inputs and power rails

Dynamically decreasing capacitance through "active copy"

Suppressing parasitic input capacitances in an op-amp circuit with series negative feedback
Suppressing the capacitance of a shielded cable through which it feeds the input signal to an operational amplifier (following shield)

Dynamically decreasing resistance by "inverting active copy" (parallel negative feedback)

Low input resistance of systems with parallel negative feedback (negative effect)

Dynamically increasing capacitance through "inverting active copy" (parallel negative feedback)

Miller effect (undesirable) in common-emitter amplifier stage
Active integrator (desired Miller effect)

Obtaining "negative" resistance by "overdosing" dynamic resistance

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