Earlier, we constructed a simple three-element oscillator using a capacitor, resistor, and a schmitt trigger inverter. It is a feedback system: the binary output of the inverter is at either the ground reference of 0 volts or at the supply voltage of 5 volts, causing the capacitor at the input to discharge or charge, respectively. The path for charging or discharging the capacitor is provided by a resistor, the value of which can be changed to alter the rate of the two events and, thereby, alter the operating frequency of the oscillator itself. In this module, we will generate circuit models for the charging and discharging events, separately, and present time-domain expressions for the voltage across the capacitor to solve for the frequency of oscillation. The models will provide you with a deeper understanding of feedback loops as you learn about relaxation-oscillator analysis