Chapter 26, Problem 90GP

Figure 26–79 shows the circuit for a simple sawtooth oscillator. At time t = 0, its switch S is closed. The neon bulb has initially infinite resistance until the voltage across it reaches 90.0 V, and then it begins to conduct with very little resistance (essentially zero). It stops conducting (its resistance becomes essentially infinite) when the voltage drops down to 65.0 V. (a) At what time t₁ does the neon bulb reach 90.0 V and start conducting? (b) At what time t₂ does the bulb reach 90.0 V for a second time and again become conducting? (c) Sketch the sawtooth waveform between t = 0 and t = 0.70 s.

FIGURE 26–79 Problem 90.