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The Shockwave at the
end of this page lets you try out how Interactive Lab works.
Introduction: To illustrate Interactive Laboratory, this demo will walk through the steps a student would take in completing a laboratory exercise. This demo will examine the Saw-tooth Waveform Generator laboratory. In the laboratories, a student is expected to compute component values for a given circuit that will satisfy a predetermined set of design specifications. For the Saw-tooth laboratory the circuit used is shown below with the components to be calculated highlighted.
This circuit should generate the waveform v3(t) from input v5(t) as shown below.
Ciruit Theory: A constant voltage v1 = -15 Volts applied to resistor R produces a constant current I = ‑v1/R circulating R from right to left. The additional path this current will flow depends on the state if transistor Q, which operates as a switch (connected in parallel with capacitor C), driven on and off by square-wave input voltage v5. When switch Q is open, constant current I flows through C, charging it linearly with time, according to the equation v3 = I·t/C. When Q is turned off, C quickly discharges through Q, and I flows now through closed switch Q, which makes v3 remain equal to zero.
With above explanation, and adopting a current I = 10 mA and an over-saturation factor OS » 10 for Q, the student should be able to come up with the following component values: R = 1.5 kW, C = 0.2 mF and Rb = 2.2 kW.