Analog Electronics

Welcome to the world of Analog Electronics — the foundation of all modern circuitry. Here you’ll learn how continuous signals, voltages, and currents form the basis for amplification, measurement, and control in countless applications.

From simple resistors and capacitors to complex operational amplifiers, analog circuits process real-world signals such as sound, temperature, and light with precision and reliability.

Discover how filters, oscillators, and amplifiers work, learn the principles of feedback and stability, and see how analog designs integrate with digital systems in today’s mixed-signal world.

Use the menu above to explore topics, from circuit theory and signal conditioning to practical design examples. Whether you're building your first audio preamp or designing precision sensors, this section will guide you step-by-step.

Resistors Overview

A resistor is a passive electronic component that limits or regulates the flow of electric current in a circuit. It is one of the most fundamental components in electronics, used in nearly every device to control voltage, current, and signal levels. Resistors obey Ohm’s Law, which defines the relationship between voltage, current, and resistance.

Ohm’s Law

Ohm’s Law states that the voltage across a resistor is directly proportional to the current flowing through it, given by:

V = I × R

Where: V = Voltage across the resistor (Volts), I = Current through the resistor (Amperes), R = Resistance (Ohms, Ω).

Rearranging this formula allows you to calculate any one of the three quantities if the other two are known.

Resistor Color Code

Fixed resistors often use color bands to indicate their resistance value and tolerance. This color-coding system is a standardized way to quickly identify resistor values without measuring them. The color bands correspond to digits and multipliers according to the Resistor Color Code Chart.

Resistor color code example

How to Read the Color Code

First Band: Represents the first significant digit.
Second Band: Represents the second significant digit.
Third Band: Represents the multiplier (power of 10).
Fourth Band: Indicates the tolerance (accuracy).

Example for a 4-band resistor:

Red (2), Violet (7), Yellow (×10⁴), Gold (±5%) → 270kΩ ±5%

Color Code Chart

Color	Digit	Multiplier	Tolerance
Black	0	×1	—
Brown	1	×10	±1%
Red	2	×100	±2%
Orange	3	×1,000	—
Yellow	4	×10,000	—
Green	5	×100,000	±0.5%
Blue	6	×1,000,000	±0.25%
Violet	7	×10,000,000	±0.1%
Gray	8	×100,000,000	±0.05%
White	9	×1,000,000,000	—
Gold	—	×0.1	±5%
Silver	—	×0.01	±10%
None	—	—	±20%

E-Series and Accuracy

Resistors are manufactured according to standard value series known as E-series, defined by the IEC standard. The series corresponds to the resistor’s tolerance level.

E6: ±20% tolerance
E12: ±10% tolerance
E24: ±5% tolerance
E48: ±2% tolerance
E96: ±1% tolerance
E192: ±0.5% or better

Common Types of Resistors

Resistors come in several types, each optimized for specific electrical and environmental conditions. Below are the most common resistor types used in electronics:

Carbon Composition Resistors

Made of a carbon powder and binder mixture, these resistors were once widely used but are now less common due to poor tolerance and noise performance. They are still valued for their high energy surge capability.

Carbon Film Resistors

These consist of a thin film of carbon deposited on a ceramic substrate. They offer improved tolerance and stability over carbon composition types and are widely used in general-purpose circuits.

Metal Film Resistors

Using a thin metal layer instead of carbon, these resistors provide excellent accuracy, low noise, and high temperature stability. Common tolerances range from 1% to 0.1%.

Wirewound Resistors

Constructed by winding a resistive wire (usually nickel-chromium) on a ceramic core, these are capable of dissipating high power. They are typically used in power supplies, amplifiers, and high-precision circuits.

Variable Resistors (Potentiometers & Trimmers)

Variable resistors allow adjustment of resistance. Potentiometers are used for manual control (like volume knobs), while Trimmer resistors are used for fine-tuning during calibration.

Resistor Power Rating

Each resistor can dissipate only a certain amount of power as heat before it is damaged. The power rating is calculated by:

P = V × I = I² × R = V² / R

Common ratings include 0.25W, 0.5W, 1W, 2W, and higher for power resistors. Always choose a resistor with a power rating at least twice the expected dissipation for reliability.

Applications of Resistors

Current limiting in LED and sensor circuits
Voltage dividers
Biasing of transistors
Feedback and gain control in amplifiers
Load resistors and test circuits

Practical Examples

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Understanding Resistor Characteristics

Resistors exhibit various electrical and physical characteristics that influence their performance in a circuit. These include tolerance, temperature coefficient, noise, and long-term stability.

1. Tolerance

Tolerance defines how close the actual resistance value is to the nominal value. For example, a 1 kΩ ±5% resistor may have a true resistance between 950 Ω and 1050 Ω.

2. Temperature Coefficient

The resistance of most materials changes slightly with temperature. The Temperature Coefficient of Resistance (TCR) is measured in parts per million per degree Celsius (ppm/°C) and indicates how stable the resistor is over varying temperatures.

3. Noise

Resistors generate electrical noise, especially at high frequencies. Metal film and wirewound resistors produce the least noise, while carbon composition resistors produce the most.

4. Stability and Aging

Over time, resistors may drift from their original values due to environmental stress, humidity, and thermal cycling. High-precision resistors are designed to minimize this drift.

Learn more about precision resistors

Capacitors Overview

A capacitor is a passive electronic component that stores electrical energy in an electric field. It consists of two conductive plates separated by an insulating material called a dielectric. When voltage is applied, charge accumulates on each plate, creating a potential difference. Capacitors are widely used for filtering, timing, coupling, smoothing, and energy storage.

Basic Principle

The amount of charge a capacitor can store is proportional to the voltage across it, described by:

Q = C * V

Where:

Q = charge (coulombs)
C = capacitance (farads)
V = voltage (volts)

The current through a capacitor is related to the rate of voltage change:

I = C * (dV/dt)

Capacitor Symbols and Appearance

Capacitors are represented in schematics as two parallel lines (for non-polarized types) or one curved line (for polarized types). They can appear as small ceramic disks, electrolytic cylinders, or large can-style capacitors in power circuits.

Capacitors

Capacitance Coding and Markings

Capacitors use numerical or color codes to indicate capacitance values, typically in picofarads (pF). A common three-digit code uses the first two digits as significant figures and the third as a multiplier.

Example Code	Meaning	Capacitance
104	10 × 10⁴ pF	100 nF
473	47 × 10³ pF	47 nF
222	22 × 10² pF	2.2 nF

E-Series and Tolerance

Capacitors are manufactured in standard E-series (E6, E12, E24, etc.) like resistors and inductors. Typical tolerances range from ±20% for electrolytic types to ±1% for precision film capacitors.

Types of Capacitors

Ceramic Capacitors: Small, inexpensive, low ESR, used for decoupling and RF applications.
Electrolytic Capacitors: High capacitance, polarized, used for power filtering.
Tantalum Capacitors: Compact polarized capacitors with stable characteristics.
Film Capacitors: Non-polarized, stable over a wide temperature range, good for timing circuits.
Supercapacitors: Very high capacitance for energy storage or backup power.
Variable Capacitors: Tunable types used in radio frequency circuits.

Practical Examples

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Charging and Discharging

A capacitor charges exponentially when connected through a resistor to a voltage source.


// Voltage across capacitor during charging:
// V(t) = V_supply * (1 - e^(-t / (R*C)))

float R = 10000.0; // 10kΩ
float C = 0.000001; // 1µF
float tau = R * C; // Time constant 0.01 s
Serial.println(tau);

RC Timing Circuit

In a timer or pulse generator, the capacitor defines delay time with the resistor.


// Time delay = 1.1 * R * C
float R = 47000.0; // 47kΩ
float C = 0.000001; // 1µF
float delayTime = 1.1 * R * C; // 0.0517 s
Serial.println(delayTime);

AC Coupling / Signal Blocking

Capacitors allow AC signals to pass while blocking DC, making them ideal for coupling amplifier stages.


// Reactance Xc = 1 / (2πfC)
float f = 1000.0; // 1 kHz
float C = 0.000001; // 1µF
float Xc = 1 / (2 * 3.1416 * f * C); // 159.15 Ω
Serial.println(Xc);

Smoothing in Power Supply

Large electrolytic capacitors are used to smooth rectified DC voltage.


// Ripple voltage approximation: Vr = I / (f * C)
float I = 0.1; // 100 mA load
float f = 100.0; // 100 Hz ripple
float C = 0.001; // 1000 µF
float Vr = I / (f * C); // 1V ripple
Serial.println(Vr);

LC Resonance

A capacitor and inductor together form a resonant circuit with frequency determined by L and C.


// Resonant frequency f = 1 / (2π√(L*C))
float L = 0.001; // 1 mH
float C = 0.000001; // 1 µF
float f = 1 / (2 * 3.1416 * sqrt(L * C)); // ≈ 5032 Hz
Serial.println(f);

Inductors Overview

An inductor is a passive electronic component that stores energy in a magnetic field when current flows through it. It resists changes in current, making it essential in filters, power supplies, oscillators, and RF circuits. The unit of inductance is the henry (H).

Basic Principle

When current through a coil changes, the magnetic field around it also changes, inducing a voltage that opposes the current change. This is described by Faraday’s Law of Electromagnetic Induction:

V = L * (di/dt)

Where:

V = induced voltage (volts)
L = inductance (henrys)
di/dt = rate of change of current (amperes per second)

Inductor Symbols and Appearance

Inductors are usually shown in schematics as coiled lines. They may look like small wound coils or ferrite components in real circuits.

Inductors

Inductance Values and Coding

Just like resistors, some inductors use color bands or printed codes to indicate their value. The color code is similar but uses microhenries (µH) instead of ohms.

Color	Digit	Multiplier
Black	0	x1
Brown	1	x10
Red	2	x100
Orange	3	x1,000
Yellow	4	x10,000
Green	5	x100,000
Blue	6	x1,000,000
Violet	7	x10,000,000
Gray	8	x100,000,000
White	9	x1,000,000,000

E-Series and Tolerance

Inductors follow standard E-series values like resistors — commonly E6, E12, or E24 — with tolerances from ±10% down to ±2%.

Types of Inductors

Air-core: No magnetic material; best for high-frequency circuits.
Iron-core: High inductance; used in low-frequency applications.
Ferrite-core: Common in SMPS and RF filters; efficient at high frequencies.
Toroidal: Ring-shaped core with low magnetic leakage.
Variable Inductors: Adjustable inductance using movable cores.
Chokes: Inductors designed to block AC while passing DC.

Practical Examples

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Inductor Charging and Energy Storage

When current through an inductor increases, energy is stored in its magnetic field.


// Energy stored in an inductor
float L = 0.01; // 10 mH
float I = 0.5;  // 0.5 A
float Energy = 0.5 * L * I * I; // 0.00125 J
Serial.println(Energy);

RL Circuit Time Constant

The time constant of an RL circuit determines how fast current builds up or decays.


// Time constant τ = L / R
float L = 0.1;   // 100 mH
float R = 10.0;  // 10 Ω
float tau = L / R; // 0.01 seconds
Serial.println(tau);

Low-Pass LC Filter

A simple LC circuit can smooth voltage by filtering high-frequency noise.


// Cutoff frequency f = 1 / (2π√(L*C))
float L = 0.00047; // 470 µH
float C = 0.000001; // 1 µF
float f = 1 / (2 * 3.1416 * sqrt(L * C)); // ≈ 232 Hz
Serial.println(f);

Transformer Inductance Relation

Primary and secondary inductances are related by the turns ratio squared.


// L2 = L1 * (N2/N1)^2
float L1 = 1.0; // 1 H primary
float N1 = 100;
float N2 = 200;
float L2 = L1 * pow(N2 / N1, 2); // 4 H secondary
Serial.println(L2);

Diodes Overview

A diode is a semiconductor device that allows current to flow in one direction only. It is made of a p-n junction that conducts when forward-biased and blocks current when reverse-biased. Diodes are essential in rectification, voltage regulation, switching, signal modulation, and many other electronic applications.

Basic Principle

When a diode is forward-biased (positive voltage on the anode relative to the cathode), current flows once the voltage exceeds the threshold or forward voltage drop:

I ≈ I₀ * (e^(Vd / (n * Vt)) - 1)

Where:

I = diode current
I₀ = reverse saturation current
Vd = voltage across the diode
n = ideality factor (typically 1–2)
Vt = thermal voltage (~26 mV at 300K)

Symbol and Appearance

A diode’s schematic symbol shows the direction of conventional current flow (from anode to cathode). The cathode is marked with a stripe on physical diodes.

Diode symbol

Physical diodes

Key Parameters

Forward Voltage Drop (Vf): The voltage required to turn on the diode (≈0.7 V for silicon, ≈0.3 V for germanium, ≈0.2 V for Schottky).
Reverse Breakdown Voltage (Vz): The voltage at which reverse current rapidly increases.
Reverse Recovery Time (trr): The time needed for a diode to stop conducting after switching off.
Maximum Forward Current (If): The highest continuous forward current rating.

Common Diode Types

Type	Purpose	Typical Use
Rectifier Diode	Allows DC from AC	Power supplies
Zener Diode	Reverse breakdown voltage regulation	Voltage regulators
Schottky Diode	Low forward drop, fast switching	Power conversion, RF
LED	Emits light when forward-biased	Indicators, displays
Photodiode	Generates current from light	Optical sensors
Varactor (Varicap)	Voltage-controlled capacitance	RF tuning
Tunnel Diode	Negative resistance region	Oscillators, microwave circuits
Gunn Diode	Microwave oscillator without p-n junction	Radar, transmitters

Practical Examples

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Half-Wave Rectifier

A single diode allows only the positive half-cycles of an AC signal to pass, converting AC to pulsed DC.


// Simple half-wave rectifier simulation
float Vin = 10.0 * sin(phase); // AC input
float Vout = (Vin > 0.7) ? Vin - 0.7 : 0.0;
Serial.println(Vout);

Zener Voltage Regulation

A Zener diode maintains a constant voltage across its terminals when reverse-biased beyond its breakdown voltage.


// Simple zener regulator model
float Vin = 12.0;
float R = 220.0; // series resistor
float Vz = 5.1;
float Iz = (Vin - Vz) / R;
Serial.println(Iz);

Schottky Fast Switching

Schottky diodes have low forward voltage (~0.2 V) and are ideal for high-speed switching circuits.


// Example forward voltage comparison
float Vf_silicon = 0.7;
float Vf_schottky = 0.2;
float efficiency_gain = (Vf_silicon - Vf_schottky) / Vf_silicon * 100.0;
Serial.println(efficiency_gain); // ~71% less drop

LED Forward Bias

LEDs emit light when forward-biased. The current must be limited by a resistor.


// LED current-limiting resistor
float Vs = 5.0;
float Vf = 2.0;
float If = 0.02; // 20 mA
float R = (Vs - Vf) / If; // 150 Ω
Serial.println(R);

Photodiode Current

Photodiodes generate a current proportional to the light intensity.


// Photodiode model
float lightIntensity = 100.0; // arbitrary units
float sensitivity = 0.5; // µA per lux
float Iphoto = lightIntensity * sensitivity; // µA
Serial.println(Iphoto);

Varactor Tuned Oscillator

A varactor diode acts as a voltage-controlled capacitor, tuning the frequency of an LC oscillator.


// Varactor capacitance example
float Vbias = 5.0;
float C0 = 50e-12; // 50 pF
float Vj = 0.7;
float m = 0.5;
float Cvar = C0 / pow(1 + Vbias / Vj, m);
Serial.println(Cvar);

Gunn Diode Oscillator

Gunn diodes generate microwave oscillations by negative differential resistance in a semiconductor without a p-n junction.
```
// Gunn diode frequency approximation
float domainTransitTime = 1e-12; // s
float f = 1 / domainTransitTime; // 1 THz
Serial.println(f);
        
```

Transistor Overview

A transistor is a semiconductor device used to amplify or switch electrical signals and power. It can control a large current with a small input current or voltage, making it one of the most important components in modern electronics.

Basic Principle

Transistors operate as controlled current or voltage gates. There are two main categories:

Bipolar Junction Transistors (BJT): Current-controlled devices (Base current controls Collector current).
Field Effect Transistors (FET): Voltage-controlled devices (Gate voltage controls Drain current).

NPN transistor symbol

Key Equations


// BJT (current-controlled)
Ic = β * Ib

// MOSFET (voltage-controlled, saturation region)
Id = k * (Vgs - Vth)^2

β = current gain (BJT)
k = transconductance constant (MOSFET)
Vgs = gate-to-source voltage
Vth = threshold voltage

Symbol and Terminals

Each transistor has three terminals:

BJT: Base (B), Collector (C), Emitter (E)
MOSFET: Gate (G), Drain (D), Source (S)

MOSFET symbol

Common Transistor Types

Type	Control Mechanism	Applications
NPN / PNP BJT	Current-controlled	Amplifiers, switches
N-Channel / P-Channel MOSFET	Voltage-controlled	Power switching, logic circuits
JFET	Reverse-biased gate voltage	Analog amplifiers
IGBT	Voltage-controlled hybrid (MOSFET + BJT)	High power converters
Darlington Pair	Two BJTs cascaded for high gain	Power drivers
Phototransistor	Light intensity controlled	Optical sensors

Key Parameters

β (hFE): Current gain (Ic/Ib for BJTs)
Vce(sat): Collector-Emitter saturation voltage
Vgs(th): Gate threshold voltage for MOSFETs
Rds(on): On-state resistance of MOSFET
fT: Transition frequency (gain drops to unity)

Practical Examples

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BJT as a Switch

A BJT can be used to turn loads ON or OFF using a small base current.


// BJT switching circuit
float Vcc = 5.0;
float Rb = 10000.0; // base resistor
float Ib = 0.0005; // 0.5 mA
float beta = 100.0;
float Ic = beta * Ib;
Serial.println(Ic); // expected collector current

BJT Amplifier

The transistor amplifies small input voltages by controlling collector current through base current.


// Voltage gain (approximate)
float Rc = 4.7e3;
float Re = 1.0e3;
float Av = Rc / Re; // gain ≈ 4.7
Serial.println(Av);

MOSFET Logic-Level Control

A logic-level MOSFET can be directly driven from a microcontroller GPIO pin.


// Logic-level MOSFET drive
int gatePin = 9;
int loadPin = 13;

void setup() {
  pinMode(gatePin, OUTPUT);
  pinMode(loadPin, OUTPUT);
}

void loop() {
  digitalWrite(gatePin, HIGH); // Turn MOSFET ON
  delay(1000);
  digitalWrite(gatePin, LOW);  // Turn MOSFET OFF
  delay(1000);
}

JFET Bias Example

JFETs use gate-source voltage to control current flow through the channel.


// JFET drain current calculation
float Idss = 10e-3;
float Vgs = -2.0;
float Vp = -5.0;
float Id = Idss * pow(1 - Vgs / Vp, 2);
Serial.println(Id);

IGBT Power Switch

IGBTs combine the high input impedance of a MOSFET with the current handling of a BJT.


// Power dissipation in IGBT
float Ic = 20.0; // A
float Vce_sat = 1.5; // V
float Pd = Ic * Vce_sat;
Serial.println(Pd); // 30 W

Darlington Pair Gain

Two transistors connected to multiply current gain: β_total = β₁ × β₂.


float beta1 = 100.0;
float beta2 = 150.0;
float beta_total = beta1 * beta2;
Serial.println(beta_total); // 15000

Phototransistor Light Sensor

Phototransistors use light intensity to control collector current, ideal for light detection circuits.


// Light-based collector current
float light = 300.0; // arbitrary units
float sensitivity = 10e-6; // A per lux
float Ic = light * sensitivity;
Serial.println(Ic);

DIAC, TRIAC, THYRISTOR & Gate-Turn-Off (GTO) Devices

These four device families form the backbone of solid-state AC and DC power control. Emerging from early developments in semiconductor rectifiers in the 1950s and 60s, they replaced bulky mechanical relays, variable transformers, and contactors with compact, reliable electronic switches capable of handling kilowatts of power.

DIAC — Bidirectional Trigger Device

The DIAC (Diode for Alternating Current) is a two-terminal bidirectional semiconductor device used primarily as a trigger for TRIACs. It behaves like two inverse-parallel diodes with a sharp breakdown characteristic. When the voltage across the DIAC exceeds its breakover voltage (typically 28–36 V), it suddenly conducts, allowing a rapid pulse of current to pass and triggering the connected TRIAC into conduction.

History: The DIAC was developed in the 1960s as a companion device to the TRIAC, which required a consistent triggering pulse for reliable AC switching. By providing symmetrical conduction in both polarities, DIACs ensured flicker-free dimming and smoother phase control.

Applications:
- Triggering TRIACs in lamp dimmers and motor speed controllers.
- Providing stable firing angles independent of load variations.
- Voltage threshold sensing in AC control circuits.
```
// Simulated DIAC triggering threshold
float Vin = 30.0;     // AC voltage peak
float Vbreak = 32.0;  // DIAC breakover voltage
bool conducting = false;

if (Vin >= Vbreak || Vin <= -Vbreak) {
    conducting = true;  // Device conducts in both polarities
}
        
```
TRIAC — Bidirectional AC Power Controller

The TRIAC (Triode for Alternating Current) is a three-terminal semiconductor switch that conducts current in both directions when triggered. It is essentially a pair of thyristors (SCRs) connected in inverse parallel within a single package, sharing a common gate terminal.

History: Invented in the mid-1960s, the TRIAC allowed control of AC power without rectification, enabling compact and cost-effective solutions for dimming and motor speed control. Early devices were used in domestic lighting dimmers and electric fan controllers.

Applications:
- Light dimmers for resistive loads.
- Speed control of universal motors (e.g., drills, fans).
- Heater control in temperature regulators.
- Solid-state relays for AC mains control.
```
// Simulate TRIAC firing angle control
float angle = 60.0;  // Trigger angle in degrees
float Vpeak = 325.0; // Peak of 230V RMS AC
float conductionFraction = (180.0 - angle) / 180.0;
float Vrms = Vpeak * sqrt(conductionFraction) / sqrt(2.0);
        
```
Thyristor (SCR) — Controlled Rectifier

The Thyristor, or Silicon Controlled Rectifier (SCR), is a four-layer PNPN semiconductor that behaves like a diode with a controllable switch. Once triggered by a small gate current, it continues to conduct until the current falls below its holding current.

History: The SCR was developed by General Electric in 1957 under the leadership of Gordon Hall and is often regarded as the first practical solid-state power switch. It quickly replaced vacuum tubes and mercury arc rectifiers in industrial power systems.

Applications:
- Controlled DC power supplies and rectifiers.
- AC motor speed control and soft starters.
- Phase-controlled converters and inverters.
- Overvoltage crowbar protection circuits.
```
// Simple SCR conduction model
bool gate = true;
float current = 5.0;
float holding = 1.0;
bool conducting = false;

if (gate) conducting = true;
if (current < holding) conducting = false;
        
```
GTO — Gate Turn-Off Thyristor

The Gate Turn-Off Thyristor (GTO) is an advanced variant of the SCR that can be turned on by a positive gate pulse and turned off by a negative gate current. This allows full gate control without needing to reduce the anode current externally.

History: Introduced in the early 1970s, the GTO represented a major advance in high-power control for traction systems and large inverters. It preceded the IGBT era, providing efficient switching at hundreds of amperes and kilovolts, though requiring strong gate drive circuits.

Applications:
- Traction motor control (electric locomotives).
- High-power DC-AC inverters.
- Industrial drives and choppers.
- Solid-state circuit breakers.
```
// GTO turn-on and turn-off control
bool gateOn = true;
bool gateOff = false;
bool conducting = false;

if (gateOn) conducting = true;   // Trigger ON
if (gateOff) conducting = false; // Force OFF
        
```
TRIAC + DIAC Light Dimmer Example

The DIAC provides a sharp trigger to the TRIAC once the RC timing capacitor reaches the DIAC’s breakdown voltage. By adjusting the resistance, the capacitor charges at a different rate, altering the phase angle and therefore the brightness of a connected lamp.

Use case: Common household light dimmers and heater controllers.
```
// RC time-based trigger simulation
float R = 10000.0;   // 10kΩ
float C = 0.1e-6;    // 0.1μF
float Vbreak = 30.0; // DIAC trigger voltage
float Vc = 0.0;
float t = 0.0;
float dt = 1e-4;

while (Vc < Vbreak) {
    Vc += (230.0 * sin(t * 2 * PI * 50)) * (dt / (R * C));
    t += dt;
}
        
```

Summary Comparison

Device	Control Type	Polarity	Main Use	Introduced
DIAC	Breakover (no gate)	Bidirectional	Trigger for TRIACs	1960s
TRIAC	Gate-triggered	Bidirectional	AC power control	1964
Thyristor (SCR)	Gate-triggered	Unidirectional	DC & AC power conversion	1957
GTO	Gate turn-on/turn-off	Unidirectional	High-power switching	1970s

Operational Amplifiers (Op-Amps)

An Operational Amplifier is a high-gain electronic voltage amplifier with differential inputs (inverting and non-inverting) and usually a single-ended output. Op-Amps are fundamental building blocks for analog circuits including amplifiers, filters, integrators, and oscillators.

History & Background

The concept of an Op-Amp originated in the 1940s for analog computers, performing mathematical operations like addition, subtraction, integration, and differentiation. Early devices were vacuum-tube based, but modern IC Op-Amps (like the 741, LM324) became popular in the late 1960s. They provide very high input impedance, low output impedance, and large open-loop gain.

Op-Amp Configurations

The most common configurations are:

Inverting amplifier
Non-inverting amplifier
Low-pass filter
High-pass filter

Practical Calculator Dialogs

Click a configuration below to open a calculator for gain or cutoff calculations:

Inverting Amplifier Calculator

Gain formula: Gain = -Rf / Rin
Rin (Ω): Rf (Ω):
Gain:
Non-Inverting Amplifier Calculator

Gain formula: Gain = 1 + Rf / Rin
Rin (Ω): Rf (Ω):
Gain:
Low-Pass Filter Calculator

Cutoff frequency formula: f_c = 1 / (2π R C)
R (Ω): C (F):
f_c: Hz
High-Pass Filter Calculator

Cutoff frequency formula: f_c = 1 / (2π R C)
R (Ω): C (F):
f_c: Hz

Summary of Op-Amp Configurations

Configuration	Gain Formula	Use Cases
Inverting Amplifier	Gain = -Rf / Rin	Signal inversion, audio preamps, summing amplifier
Non-Inverting Amplifier	Gain = 1 + Rf / Rin	Buffering, precision amplification
Low-Pass Filter	f_c = 1 / 2πRC	Noise reduction, anti-aliasing, audio filtering
High-Pass Filter	f_c = 1 / 2πRC	AC coupling, signal differentiation, bass cut in audio

Common Analog ICs

Analog Integrated Circuits (ICs) are semiconductor devices designed to process continuous voltage or current signals. Unlike digital ICs, analog ICs operate on a continuous range of values and are essential in signal conditioning, amplification, timing, and sensing applications.

History & Overview

Analog ICs emerged in the 1960s with the rise of monolithic integrated circuits. Early ICs were primarily for audio, instrumentation, and voltage regulation. Over the decades, ICs for oscillators, voltage references, filters, comparators, and power management have become ubiquitous in electronic systems.

Common Analog IC Families

The following are widely used analog IC types outside of operational amplifiers:

Voltage Regulators (Linear and Switching)

Voltage regulators maintain a constant output voltage despite changes in input voltage or load. Linear regulators like the 78xx/79xx series provide precise DC voltages using a pass transistor and feedback. Switching regulators (buck, boost, buck-boost ICs) achieve higher efficiency by switching current through inductors and capacitors.

History: The 78xx series was introduced in the 1970s and became the standard for low-voltage regulated supplies. Switching ICs became common in the 1980s for portable devices.

Applications: Power supplies, battery chargers, LED drivers, embedded systems.
Timer ICs

Timer ICs generate precise time delays or oscillations. The most famous example is the NE555, introduced in 1972. It can operate in monostable (one-shot), astable (oscillator), or bistable (flip-flop) modes.

Applications: Pulse-width modulation, LED flashing, clock generation, debounce circuits.
Voltage Reference ICs

Voltage reference ICs provide highly stable and precise reference voltages for ADCs, DACs, and measurement systems. Popular examples include LM336, TL431, and REF series ICs.

Applications: Precision analog-to-digital conversion, instrumentation, sensor calibration, and regulated power supplies.
Comparator ICs

Comparator ICs compare two voltages and output a digital high or low signal depending on which input is higher. They are effectively “fast zero-crossing detectors” and can replace discrete transistor comparators.

Popular ICs: LM339, LM393.

Applications: Zero-cross detection, overvoltage protection, pulse-width modulation, threshold detectors.
Phase-Locked Loop (PLL) ICs

PLL ICs synchronize an output oscillator to the frequency of an input signal. Classic examples include the 4046 CMOS PLL IC and CD4046B series.

Applications: Frequency synthesis, demodulation, clock recovery, motor speed control.
Audio Amplifier ICs

Dedicated audio amplifier ICs provide high-quality audio amplification with minimal external components. Examples include LM386 (low power), TDA2030 (medium power), and TDA7294 (high power).

Applications: Portable audio, home audio, car amplifiers, and speaker driver circuits.
Analog Multiplexer / Demultiplexer ICs

These ICs switch analog signals to a single output or distribute one input to multiple outputs. Common ICs include CD4051 (8-channel), CD4052 (4-channel), and CD4053 (triple 2-channel).

Applications: Sensor scanning, data acquisition systems, analog signal routing.
Instrumentation Amplifier ICs

Instrumentation amplifiers are designed for precise differential voltage measurements with high input impedance and excellent common-mode rejection. Examples: AD620, INA128.

Applications: Sensor signal conditioning, strain gauge measurement, ECG/EKG amplifiers.

Summary Table of Common Analog ICs

IC Type	Function	Examples	Typical Applications
Voltage Regulator	Maintain constant voltage	78xx, LM317, LM350	Power supplies, battery chargers
Timer	Time delay / oscillator	NE555, TLC555	PWM, flashing LEDs, clock generation
Voltage Reference	Provide precise voltage	LM336, TL431, REF ICs	ADC/DAC reference, calibration
Comparator	Voltage comparison	LM339, LM393	Threshold detection, zero-crossing, PWM
PLL	Frequency synthesis & lock	CD4046, LM565	Clock recovery, frequency control
Audio Amplifier	Amplify audio signals	LM386, TDA2030, TDA7294	Speakers, portable audio, car audio
Analog MUX/DEMUX	Switch analog signals	CD4051, CD4052, CD4053	Data acquisition, sensor scanning
Instrumentation Amplifier	Precision differential amplifier	AD620, INA128	Medical instrumentation, sensor interfaces

Analog Electronics

Resistors Overview

Ohm’s Law

Resistor Color Code

How to Read the Color Code

Color Code Chart

E-Series and Accuracy

Common Types of Resistors

Carbon Composition Resistors

Carbon Film Resistors

Metal Film Resistors

Wirewound Resistors

Variable Resistors (Potentiometers & Trimmers)

Resistor Power Rating

Applications of Resistors

Practical Examples

Ohm’s Law Demonstration

Voltage Divider

LED Current Limiting

Resistor Network

Variable Resistor (Potentiometer)

Understanding Resistor Characteristics

1. Tolerance

2. Temperature Coefficient

3. Noise

4. Stability and Aging

Capacitors Overview

Basic Principle

Capacitor Symbols and Appearance

Capacitance Coding and Markings

E-Series and Tolerance

Types of Capacitors

Practical Examples

Charging and Discharging

RC Timing Circuit

AC Coupling / Signal Blocking

Smoothing in Power Supply

LC Resonance

Inductors Overview

Basic Principle

Inductor Symbols and Appearance

Inductance Values and Coding

E-Series and Tolerance

Types of Inductors

Practical Examples

Inductor Charging and Energy Storage

RL Circuit Time Constant

Low-Pass LC Filter

Transformer Inductance Relation

Diodes Overview

Basic Principle

Symbol and Appearance

Key Parameters

Common Diode Types

Practical Examples

Half-Wave Rectifier

Zener Voltage Regulation

Schottky Fast Switching

LED Forward Bias

Photodiode Current

Varactor Tuned Oscillator

Gunn Diode Oscillator

Transistor Overview

Basic Principle

Key Equations

Symbol and Terminals

Common Transistor Types

Key Parameters

Practical Examples

BJT as a Switch

BJT Amplifier

MOSFET Logic-Level Control

JFET Bias Example

IGBT Power Switch

Darlington Pair Gain

Phototransistor Light Sensor

DIAC, TRIAC, THYRISTOR & Gate-Turn-Off (GTO) Devices

DIAC — Bidirectional Trigger Device

TRIAC — Bidirectional AC Power Controller

Thyristor (SCR) — Controlled Rectifier