Relaxation Oscillator

Introduction: The following explains the form by which the rectangle shape waves are attained with the support of Relaxation Oscillator.

Relaxation Oscillator:

• With affirmative feedback it becomes possible to develop relaxation oscillator that leads to formation of rectangular wave.
•  The circuit is shown in fig1.1

Fig. 1.1

• In the circuit as above, a fraction R2/ (R1 +R2) = b of the produced output is actually the feedback to the input terminal that is non-inverting.
• The procedure of the circuit can be put in plain words as follows:
• Assume that +Vsat is the output voltage. The capacitor will charge exponentially toward +Vsat.
• The feedback voltage is +bVsat. When there is a rise in the capacitor voltage, the output  +bVsat switches from +Vsat to -Vsat.
• The feedback voltage becomes -Vsat and the output will remain –Vsat.
•  Thereafter the capacitor charges in the opposite direction. When the situation arises wherein the voltage decreases below –bVsat (more negative than –bVsat) , in that case, the output again turns up +Vsat.
• This process works in continuation and leads to the production of a square wave. Under stable state conditions, the capacitor voltage and output voltage are shown in fig1.1.
• The incidence of the output can be obtained as follows:
• The capacitor charges from -ß Vsat to +ß Vsat in the phase time period T/2. The capacitor charging voltage expression is given by 123.

• In the frequency range of 10Hz to 10KHz, this square wave generator is immensely useful.
•  At elevated frequencies, the slew rate of the OPAMP confines the slope of the produced output square wave.

No comments:

Post a Comment