Astable Multivibrator - University of Minnesota （不稳多谐振荡器,明尼苏达大学）.pdf

ECE 2006 University of Minnesota Duluth Lab 7 Astable Multivibrator 1. Introduction The student will analyze and construct an astable multivibrator. The circuit will be simulated using nominal component values selected by the student to provide for specific operations. The circuit component parameters will be measured and theoretical calculations of the multivibrator’s performance will be made. The multivibrator will be constructed to observe actual perfomance. 2. Background A multivibrator is an electronic circuit used to implement a variety of simple two-state systems such as oscillators, timers and flip flops (e.g a clock signal). An astable multivibrator has two states, neither one stable. The circuit therefore behaves as an oscillator with the time spent in each state controlled by the charging or discharging of a capacitor through a resistor. The astable multivibrator may be created directly with transistors or with the use of integrated circuits such as operational amplifiers (op amps) or the 555 timer. Most operational amplifiers are powered by a positive and negative rail voltage—the output is never able to exceed these rail voltages. An example circuit is shown in Figure 1. Depending upon the inital conditions, the op amp’s output will be driven to either the positive or negative rail. Upon this occurance, the capacitor will either charge or discharge through resistor R2 (its voltage slowly rising or falling). As soon as the voltage at the op amp’s inverting terminal is Figure 1: Astable Multivibrat