Presets

💡 LED Circuit
⚡ Voltage Divider
🔋 RC Filter
🔆 Parallel LEDs
🔌 NPN Switch
🧮 Half Adder

Components

Sources

Battery
V V Source

Passives

Resistor
Capacitor
Inductor

Semiconductors

Diode
LED
NPN BJT

Logic

& AND
≥1 OR
NOT
=1 XOR

Misc

Ground
Switch
Bulb
Circuit Builder
Drag components from the palette onto the canvas. Use Wire mode to connect pins. Click a component to see its properties.

DC Circuit Analysis

Ohm's Law Calculator

Enter any two values — the third will be calculated.

Ohm's Law

V = I × R

I = V / R

R = V / I

Power: P = V × I = I² × R = V² / R

Series & Parallel Resistors

Enter resistor values separated by commas.

Combination Rules

R_series = R₁ + R₂ + ... + Rₙ

1/R_parallel = 1/R₁ + 1/R₂ + ...

Series: same current through each. Parallel: same voltage across each.

Voltage Divider

Voltage Divider

Vout = Vin × R2 / (R1 + R2)

Used to produce a lower reference voltage from a higher supply. Vout is measured at the junction of R1 and R2.

RC Time Constant

RC Circuit

τ = R × C

V(t) = V₀ × (1 − e^(−t/τ))

After 1τ the capacitor reaches ≈63.2% of Vin. Fully charged after ≈5τ.

PWM — Pulse Width Modulation

Period (T)
ON time (ton)
OFF time (toff)
Avg voltage (Vavg)
RMS voltage
Common Applications
How It Works

PWM switches a digital output ON and OFF at fixed frequency. By varying how long it stays ON (duty cycle), you control the effective average voltage seen by the load — without wasting energy in a resistor.

Key Formulas
D = ton / T
Vavg = D × Vcc
Vrms = Vcc × √D
T = 1 / f
Frequency Choice

Motor control: 1–20 kHz. LED dimming: >200 Hz (avoid flicker). Audio amplifiers: >200 kHz. Switching power supplies: 50–500 kHz. Higher frequency → smaller filter components but more switching losses.

Resolution

An 8-bit PWM timer gives 256 steps (0–255). A 10-bit timer gives 1024 steps. Arduino uses 8-bit (analogWrite 0–255). Higher resolution = finer control but more timer bits or lower max frequency.

Component Reference

Resistor

R

Opposes current flow. Unit: Ohms (Ω). V = IR. Dissipates energy as heat. Colour bands encode resistance: 4-band (2 digits + multiplier + tolerance) or 5-band for precision.

Capacitor

Stores charge; blocks DC, passes AC. Unit: Farads (F). Q = CV. Impedance Z = 1/(jωC). Common values: pF (RF), nF (signal), μF (power supply decoupling).

Inductor

Stores energy in a magnetic field; opposes changes in current. Unit: Henries (H). Impedance Z = jωL. Passes DC, blocks high-frequency AC. Used in filters and power converters.

Diode

One-way valve for current. Forward voltage drop ~0.6–0.7V (Si). Reverse-biased: blocks current until breakdown voltage. Types: signal, Zener (voltage regulation), Schottky (fast, low Vf).

LED (Light Emitting Diode)

Emits light when forward biased. Vf: red ~1.8V, green ~2.1V, blue ~3.2V. Always use a current-limiting resistor: R = (Vs − Vf) / If. Typical If: 10–20mA.

NPN Transistor (BJT)

BCE

Current amplifier / switch. Ic = β × Ib. Three regions: cutoff (off), saturation (on), active (amplifier). β (hFE) typically 50–300. Base-Emitter junction ~0.6–0.7V when active.

AND Gate

AND

Output is HIGH only when ALL inputs are HIGH. Boolean: Y = A · B. NAND is universal: any logic can be built from NAND gates alone. Used in masking, enable circuits.

OR Gate

OR

Output is HIGH when ANY input is HIGH. Boolean: Y = A + B. NOR is also universal. Used in flag detection, priority circuits, alarm systems.

NOT Gate (Inverter)

Inverts the input. Y = Ā. If input is 0, output is 1 and vice versa. The bubble symbol on any gate means inversion at that pin. CMOS inverter is the simplest logic circuit.

XOR Gate

XOR

Output is HIGH when inputs DIFFER (odd number of HIGH inputs). Boolean: Y = A ⊕ B. Key component in adders and error-checking circuits. Y=0 when A=B (comparator use).

Workshop Gallery

PCB circuit board close-up
PCB — Close-Up
Macro photo of a printed circuit board showing traces, vias, SMD components, and solder joints.
Electronics breadboard
Breadboard Prototyping
Solderless breadboards allow rapid circuit prototyping. Components plug directly into the contact holes connected by internal metal strips.
Mixed electronic components
Component Assortment
A selection of through-hole and SMD components including resistors, capacitors, transistors, and integrated circuits.
Resistors
Resistors
Carbon film and metal film resistors. Color bands encode the resistance value and tolerance. The most fundamental passive component.
Capacitors
Capacitors
Electrolytic and ceramic capacitors store charge on conductive plates separated by a dielectric. Used for filtering, decoupling, and timing.
Oscilloscope
Oscilloscope
An oscilloscope displays voltage over time. Essential for debugging circuits, measuring frequency, phase, and signal integrity.
Soldering workbench
Soldering
Soldering permanently joins components to a PCB using a tin-lead or lead-free alloy. Proper technique ensures reliable electrical and mechanical connections.