⚡ Basics & Fundamentals
8 circuits
Ohm's Law
Voltage, current and resistance in action. Adjust any component and watch the others respond instantly.
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Resistors
Resistors in a circuit. See how resistance limits current and drops voltage across each component.
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Series Resistors
Two resistors in series — same current through both, voltage divides proportionally to resistance values.
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Parallel Resistors
Resistors in parallel — same voltage across both, current divides. Total resistance less than either.
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Capacitor Charging
Capacitor charging from a voltage source. Observe the RC time constant — exponential rise, not linear.
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Inductor
Inductor in a DC circuit. Current builds up gradually as the magnetic field stores energy, collapses when switched off.
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LRC Resonant Circuit
Inductor, resistor and capacitor in series. At the resonant frequency, impedance is purely resistive — maximum current.
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Voltage Divider
Two resistors producing a fraction of the supply voltage. The most used circuit in electronics. Change R2 to vary output.
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🔊 Passive Filters
6 circuits
RC Low-Pass Filter
Passes low frequencies, attenuates high. Probe different frequencies to see rolloff above the cutoff frequency.
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RC High-Pass Filter
Blocks DC and low frequencies, passes high. Used for AC coupling between stages and 50/60Hz interference rejection.
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Band-Pass Filter
Passes a window of frequencies, attenuates both below and above. High-pass and low-pass in series.
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Notch Filter
Rejects a specific frequency band while passing everything else. Used to remove mains hum from audio signals.
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Butterworth Low-Pass
10th-order filter with maximally flat passband. Much steeper rolloff than a simple RC filter. Professional filter design.
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Loudspeaker Crossover
Splits audio into high and low frequency bands for separate drivers. The same principle used in all speaker systems.
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💡 Diodes & Rectifiers
7 circuits
Basic Diode
One-way current valve. Observe the 0.7V forward voltage drop and complete reverse blocking behaviour.
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Diode I-V Curve
Plots current vs voltage for a silicon diode. See the exponential forward curve and sharp reverse blocking threshold.
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Half-Wave Rectifier
Single diode converts AC to pulsating DC by blocking negative half-cycles. Simplest AC-to-DC converter.
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Full-Wave Bridge Rectifier
Four diodes convert both AC half-cycles to positive DC. Output frequency doubles, ripple reduces significantly.
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Rectifier with Filter Cap
Bridge rectifier with smoothing capacitor. See how the capacitor fills in the ripple to produce near-steady DC.
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Voltage Doubler
Produces DC at twice the AC peak voltage using two diodes and capacitors. No transformer needed.
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Zener Voltage Reference
Zener diode in reverse breakdown maintains a stable voltage. The simplest voltage regulator and reference circuit.
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🔬 Op-Amps
8 circuits
Op-Amp Overview
Basic op-amp open-loop. See the two inputs and single output. The differential gain amplifies the difference between inputs.
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Inverting Amplifier
Gain = -Rf/Rin. Output inverted. Change Rf to adjust gain. Input on inverting terminal through series resistor.
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Non-Inverting Amplifier
Gain = 1 + Rf/R1. Output in phase with input. High input impedance makes it ideal for sensor buffering.
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Voltage Follower
Unity gain buffer. Output equals input. Provides impedance transformation without signal attenuation.
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Summing Amplifier
Adds multiple inputs with individual gain for each. Foundation of audio mixers and weighted DAC circuits.
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Differential Amplifier
Amplifies difference between two inputs. Rejects common-mode noise. Essential for sensor interfaces.
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Schmitt Trigger
Comparator with hysteresis. Different switch-on and switch-off thresholds prevent noise-induced false triggering.
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Relaxation Oscillator
Op-amp square wave generator. Capacitor charges between Schmitt thresholds to produce continuous oscillation.
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📡 Transistors
7 circuits
NPN Transistor
BJT in basic circuit. Vary base current to see it control the much larger collector current. Current gain (h_FE) in action.
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Transistor Switch
NPN switching an LED. Small base current controls full load current. Saturation and cutoff demonstrated.
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Common-Emitter Amplifier
Classic BJT amplifier with voltage gain. Output inverted relative to input. Biased at midpoint for maximum swing.
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Darlington Pair
Two transistors cascaded to multiply current gain dramatically. h_FE1 × h_FE2. Drives high-current loads from weak signals.
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N-Channel MOSFET Switch
Voltage-controlled switch drawing near-zero gate current. Ideal for microcontroller interfaces and PWM control.
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CMOS Inverter
Complementary N and P MOSFETs forming a NOT gate. The fundamental building block of all CMOS digital logic.
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Push-Pull Output Stage
NPN and PNP in complementary pairs, amplifying both signal halves. Class B output stage for audio power amplifiers.
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⏱ 555 Timer
6 circuits
555 Astable Oscillator
Continuous square wave oscillator. Adjust R1, R2 and C to change frequency. f = 1.44 / ((R1 + 2×R2) × C).
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555 Timer Internals
Inside the 555 — comparators, flip-flop, and discharge transistor visible. Understand exactly how the IC works.
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555 Monostable
One-shot: single timed pulse when triggered. Pulse duration t = 1.1 × R × C. Returns to low automatically.
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555 PWM Generator
Pulse Width Modulator with potentiometer-controlled duty cycle. PWM output controls LED brightness or motor speed.
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555 Schmitt Trigger
555 with hysteresis. Upper threshold sets, lower threshold resets. Cleans up slow or noisy digital signals.
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555 Sawtooth Generator
Modified 555 producing sawtooth waveform instead of square wave. Useful for VCOs and audio synthesis.
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🖥 Digital Logic
8 circuits
XOR Gate
Output HIGH when inputs differ. Click the switches to verify the truth table. Core component of arithmetic circuits.
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Half Adder
Adds two 1-bit numbers. XOR gives sum, AND gives carry. The building block of all binary arithmetic circuits.
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Full Adder
Adds three 1-bit inputs (A + B + carry-in) with sum and carry outputs. Chain multiple for N-bit addition.
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D Flip-Flop
Stores one bit on rising clock edge. The fundamental memory element in all synchronous digital systems.
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JK Flip-Flop
J sets, K clears, both HIGH toggles. The most versatile flip-flop type. Used in older and educational logic design.
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4-Bit Ripple Counter
Four flip-flops counting in binary from 0 to 15. Watch the binary pattern cycle. Press reset to restart count.
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7-Segment Decoder
Converts 4-bit BCD input to seven segment display control signals. Drive numeric LED displays directly.
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SRAM Cell
Static RAM cell storing one bit with cross-coupled inverters. The basic memory element in CPU registers and L1 cache.
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⚙ Power Converters
6 circuits
Boost Converter
DC-DC step-up: output voltage higher than input. Switched inductor stores and releases energy at higher voltage.
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Buck Converter
DC-DC step-down: output lower than input. More efficient than linear regulators. Used in all modern power supplies.
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Buck-Boost Converter
Steps voltage both up and down. Output polarity inverted. Used where battery voltage varies across charge cycle.
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Cuk Converter
Buck-boost topology with non-inverted output. Two inductors reduce output ripple compared to standard buck-boost.
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Power Transmission
Why AC is transmitted at high voltage. Step-up reduces current, cutting resistive line losses dramatically.
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Step-Up Transformer
Increases AC voltage proportional to turns ratio. Output current decreases inversely — power is conserved.
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