Interactive 5-Mode Curve Tracer & Switching Simulator

📈 Interactive 5-Mode Curve Tracer & Switching Simulator

One instrument, five devices. BJT / JFET / MOSFET modes plot live characteristic curve families with a DC load line — drag the control slider and ride the green Q-point between cutoff, active/ohmic, and saturation. SCR mode is a live latching bench test, and TRIAC mode is a working phase-control dimmer.

Device Under Test

Base Current I_B 30 µA

Current Gain β 100

Fixed circuit: V_CC = 20 V, R_C = 2 kΩ → load line (20 V, 0) ↔ (0, 10 mA)

Gate Voltage V_GS −1.0 V

Device: I_DSS = 10 mA, V_P = −4 V · Circuit: V_DD = 20 V, R_D = 1.5 kΩ

Gate Voltage V_GS 3.0 V

Device: V_TH = 2 V, K = 1 mA/V² · Circuit: V_DD = 20 V, R_D = 1 kΩ

Load Current (when on) 120 mA

12 V DC supply · Holding current I_H = 30 mA. Set the load below 30 mA and try to latch it…

Firing Angle α 90°

120 VAC 60 Hz through a lamp load. Small angle = early firing = bright; large angle = late = dim.

💡 Guided Explorations

1. Ride the load line (BJT): sweep I_B from 0 → 60 µA and watch the Q-point travel from cutoff to saturation; note the readout region changing at each end. 2. β sensitivity: park I_B at 30 µA and slide β from 50 → 200 — the Q-point drifts across the entire line, which is exactly why β-dependent bias is bad design. 3. Pinch-off (JFET): start at V_GS = 0 (I_DSS) and squeeze to −4 V — the curve family collapses to zero. 4. Threshold (MOSFET): creep V_GS upward and find the exact voltage where drain current first appears — that's V_TH. 5. The latch (SCR): fire the gate, note the current keeps flowing with no gate; interrupt the anode to reset. Then set the load below 30 mA and prove it won't latch at all. 6. Dimmer (TRIAC): sweep α from 5° → 175° and watch the shaded conduction area, the power %, and the lamp glow all track together.