Electronics & Digital Systems — Logic Gates, Transistors, ADC/DAC and Signal Processing

Why Simulate Electronics?

Electronic circuits are among the most abstract engineering artifacts humans have built. A modern CPU contains billions of transistors. A WiFi frame encodes information across 52 orthogonal sub-carriers simultaneously. RF phase-locked loops synchronise to signals arriving at fractions of a radian. These are not things you can visualise by reading a datasheet.

Simulation bridges that abstraction gap. Watching a ripple-carry propagate through eight full-adder stages — seeing the carry bit light up cell by cell — installs an intuition that "carry propagation delay limits clock speed" that no textbook sentence can replicate. The same logic applies across the whole electronics stack, from Boolean gates to spectral OFDM sub-carriers.

Layer 1: Boolean Logic

Logic Gates — The Atoms of Computation

All digital logic reduces to seven primitive gates: AND, OR, NOT, NAND, NOR, XOR, and XNOR. The Logic Gates simulation renders each gate in IEEE standard symbols, animates signal pulses travelling through them, and shows a live truth table. You can chain gates manually to build combinational circuits and watch the output propagate.

A key insight the 8-bit adder makes tactile: carry propagation is the fundamental bottleneck in binary arithmetic. The signal must "ripple" through all eight full-adder stages before the result is valid. This is why real CPUs use carry-lookahead adders (CLA) or carry-select adders — they compute carry bits in parallel rather than sequentially. Understanding the ripple-carry first makes the optimisation compelling.

Layer 2: Semiconductor Devices

Transistor — The Switch That Built the World

The transistor is arguably the most important invention of the 20th century. A BJT (bipolar junction transistor) uses a small base current to control a large collector–emitter current; a MOSFET uses a gate voltage to control drain–source current without drawing base current at all. Both enable amplification and switching — the two primitive operations from which all analog and digital electronics descend.

The Bode diagram is one of the most powerful tools in electrical engineering — it shows how a circuit responds at every frequency simultaneously on a logarithmic axis. The RC filter simulation lets you tune the corner frequency by adjusting R and C, and watch the diagram update in real time. The same RC network appears in EEG amplifiers, audio crossovers, debouncing circuits, and power supply decoupling — making this one of the most universally applicable simulations in the collection.

Layer 3: Analog–Digital Interface

ADC/DAC — Bridging Two Worlds

Every microphone, camera, radio, and sensor converts a continuous analog signal into discrete digital samples — and back again. This sampling–quantisation boundary is where information theory (Nyquist's theorem) meets hardware reality (quantisation noise). The ADC/DAC simulation makes the aliasing artefact visible: sample a 900 Hz sine wave at 1000 samples/second and the output appears as a 100 Hz signal — exactly the alias predicted by Nyquist.

Quantisation noise is the fundamental price of digitisation: every analog value gets rounded to the nearest representable level. With N bits, you have 2ᴺ levels. Each additional bit doubles the number of levels and improves the signal-to-quantisation-noise ratio by roughly 6 dB. This is why professional audio uses 24-bit recording (144 dB theoretical SQNR) while consumer earbuds run 16-bit codec output (96 dB). The ADC/DAC simulator makes this trade-off tangible.

Layer 4: Digital Communications

OFDM — How WiFi and 4G Encode Data

Orthogonal Frequency Division Multiplexing is the modulation scheme used in WiFi, LTE, 5G-NR, and digital television. Instead of putting all the data on one carrier, OFDM splits the channel into dozens or hundreds of narrow sub-carriers, each carrying a small fraction of the data stream. The sub-carriers are spaced at exactly 1/T Hz apart, making them mathematically orthogonal so they don't interfere with each other — which is why an IFFT (inverse FFT) can generate them simultaneously.

The cyclic prefix in OFDM is an elegant engineering solution to a theoretical problem: a real channel produces multipath echoes that blur symbols together (intersymbol interference). By copying the last T_g seconds of each symbol to its front, OFDM turns linear convolution into circular convolution — transforming the difficult inter-symbol problem into a simple per-sub-carrier multiplication in the frequency domain. The OFDM simulation lets you toggle the cyclic prefix on and off and watch the constellation scatter as multipath destroys orthogonality without it.

Complete Electronics Collection

Algorithms & Methods