A Darlington pair connects two BJT stages to obtain high effective current gain. A tiny modeled touch current can therefore control a visible load.
1. Set up the experiment
Increase the synthetic touch input from zero. Compare one transistor with the paired high-gain mode.
2. Connect the result to the equation
β_eff ≈ β1β2; V_BE,total ≈ 1.4 V
Change one parameter at a time and keep the others fixed. Read the signed output and current, then use the curve to distinguish a steady relationship from a changing transient.
Initial supply
5.00 V
Initial current
0.010 mA
Initial output
4.998 V
3. Notice the limits
This is a virtual touch source, not a body-current experiment. A Darlington has a larger base-emitter drop and saturation limitations than a single BJT.
Circuit reference diagram
Continue this learning path
Why it’s here
Electronics 101 makes a component change visible: an altered resistance changes a current, a capacitor changes a delay, and a sensor changes a decision. The course guide links each concept to its experiment.
Open Ohm’s law and predict the effect of doubling the voltage.
Change the control and compare the ammeter, curve and equation.
Try RC charging and use the time constant to explain the curve.
Return to the course guide to choose the next experiment.
Frequently asked questions
Can I use every experiment on NavSprout?
Yes. The course guides and workbenches run on NavSprout.
Are these circuit simulations exact?
They are analytic teaching models: ideal sources and switches, fixed diode drops, simple BJT gain and saturation, exponential RC behavior, and illustrative sensor curves. They are not a SPICE solver or construction verification.
Do I need hardware or a login?
No hardware or account is needed. The 3D view needs WebGL, while diagrams, controls and static lessons remain available as alternatives. Progress is stored in this browser and can be exported.
Which current direction is shown?
Moving markers represent conventional current, not electron drift. Their motion is illustrative and is not a measurement of charge velocity.
Model references and scope
Original NavSprout lessons use standard lumped-circuit relationships and explicitly simplified component models. Diagrams explain teaching topologies, while the breadboard probe explains socket continuity. The workbench is not a verified physical assembly plan.
