Improved Phase Shift Oscillator

Average current draw - 6.5mA Expected life of 9V battery - 3days,5hours For a 500mAh battery Power draw - 60mW Upk-pk - 4.66V Um - 2.35V Ueff (RmS) - 1.66V Frequency - 426Hz-470Hz (varies to much) Output impedance - Depends on the final stage setup and is 3.3K in the case. How this oscillators work is by using the collector output to provide 180 degrees phase shift that goes through a series of RC filters phase shift network and gets delayed by another half cycle. That gives a total of 360 degrees that makes up the needed positive feedback to start the oscillations. The emitter potentiometer is to fine adjust the strength of the negative feedback to a level that would kickstart the oscillations. I really recommend it if you're trying to build this because these oscillators are not easy to start from the first go and they require some tweeking. The deployment of the RC phase shift network is crucial because without their 180 degrees phase shift you won't have a full positive feedback to jumpstart the oscillations. The transistors can be of any kind. With overall draw of 9mA all kinds of low power transistors will do. I recommend the BCxxx series like bc550. The frequency is given by the formula f=1/2п.square root of 6.RC

published 11 years ago