Online Circuit Simulation Lab
Build and simulate circuits right in your browser — no hardware, no install. Drag components, watch voltages and currents come alive, then source every part or turn the design into a BOM in one click.
- ✓ Analog, digital, op-amp, 555 & power circuits
- ✓ Each part links to live stock & pricing
- ✓ One-click BOM for quoting & ordering
Ohm's Law
The most fundamental relationship: Voltage = Current × Resistance (V=IR). Vary the source and resistor and watch the current respond.
Resistors in Series
Resistors connected end-to-end: total resistance is the sum, and the same current flows through each.
Resistors in Parallel
Resistors side by side share the same voltage; currents add and the equivalent resistance drops below the smallest branch.
Voltage Divider
Two resistors scale an input voltage by ratio — the workhorse behind sensor sampling, level shifting and potentiometers.
Capacitor Charging (RC)
A capacitor charges and discharges through a resistor along an exponential curve; the time constant τ=RC sets the pace.
Inductor Kickback & Flyback Diode
Interrupting inductor current creates a large voltage spike; a flyback (freewheeling) diode protects the switching transistor.
Driving an LED (Current Limiting)
An LED always needs a series current-limiting resistor: R = (Vsupply − Vf) / If. Without it the LED burns out.
BJT Transistor Switch
Drive an NPN BJT between saturation and cut-off so a small base current switches a larger load current.
Common-Emitter Amplifier
The classic single-transistor voltage amplifier: bias resistors set the Q-point and the signal is amplified (inverted) at the collector.
MOSFET Switch
A MOSFET is voltage-controlled with almost zero gate current, ideal for high-current, high-frequency switching in power and motor drives.
Zener Voltage Reference
In reverse breakdown a Zener holds a constant voltage; with a series resistor it forms a simple reference or regulator.
Voltage Follower (Buffer)
Output tied to the inverting input gives unity gain with very high input and very low output impedance — a classic buffer.
Inverting Amplifier
The canonical op-amp stage with gain = −Rf/Rin and an inverted output.
Non-Inverting Amplifier
Signal enters the non-inverting input; gain = 1+Rf/Rg, output is in phase with very high input impedance.
Summing Amplifier
Multiple input currents sum at the inverting node, producing a weighted sum — the basis of analog computing and audio mixing.
CMOS Inverter
A PMOS and an NMOS form the basic NOT gate — and reveal why static CMOS draws almost no current.
Half Adder
An XOR plus an AND gate add two 1-bit numbers into Sum and Carry — the starting point of every ALU.
7-Segment Decoder Driver
A decoder turns a BCD/binary code into seven-segment drive signals — the classic digital display chain.
555 Astable Oscillator (Blinker)
An NE555 in astable mode self-oscillates into a square wave via two resistors and a capacitor; the RC values set the blink period.
Full-Wave Bridge Rectifier
Four diodes route both AC half-cycles in one direction; a capacitor then smooths it to DC — the first stage of nearly every supply.
Buck (Step-Down) Converter
A switch, inductor, diode and capacitor efficiently step a higher DC voltage down — the most common board-level supply topology.
Frequently Asked Questions
Does the simulator require install or payment?
No. It runs entirely in the browser, is free, and works on desktop and mobile — ideal for students, makers and engineers to validate circuits quickly.
How do I buy the parts used in a simulation?
Every guided circuit lists its components. Click “Find stock” to search 15M+ parts with live inventory, pricing and supplier comparison, or generate a BOM in one click for quoting.
Can simulation results be used directly for production?
The lab is for learning, principle verification and early evaluation with idealized/simplified models. For production, rely on datasheet parameters, SPICE models and real prototyping.
The simulator is powered by the open-source CircuitJS1 project (GPL-2.0, by Paul Falstad & Iain Sharp), self-hosted and isolated in an iframe. View source code
MCU simulation uses avr8js (MIT, by Uri Shaked / Wokwi), self-hosted. avr8js