Fig1.3 RC phase shift oscillator Note: C4= 0.47uf is connected internally You can see variable pot on the trainer board its value is 1K, using of this pot shaping of input wave. In the circuit diagram resistor R1 and the resistor R (close to the base of Q1 in the diagram) gives a voltage divider bias to the transistor Q1. Resistor Rc limits the collector current while Re is meant for thermal stability. Ce is the emitter by-pass capacitor and Cout is the output DC decoupling capacitor. By using more than three RC phase shift stages (like 4 x 45°) the frequency stability of the oscillator can be further improved. The frequency of the transistor RC phase shift oscillator oscillator can be expressed by the equation: Where F is the frequency, R is the resistance, C is the capacitance and N is the number of RC phase shift stages. The RC pahse shift oscillator can be made variable by making the resistors or capacitors variable. The common approach is to leave the resistors untouched the three capacitors are replaced by a triple gang variable capacitor. www.mineinstruments.in 3 1 F= 2 √ + ( ) Where, R=390Ω C = 0.012uf R6 =1k Ω 1 F= 2 . √ + ( ) Theoretical = 8.43 KHz Due to tolerance of components values, theoretical & practical values varry ±10% ǁǁ § § § ǁǁ www.mineinstruments.in 4