Wien Bridge Oscillator: Kukurin Kirkiro da Cikakken Adadin Daɗi

Mau yadda Wien Bridge Oscillator shi da?

Wien-Bridge Oscillator wani abu ne na phase-shift oscillator wanda ake gina ta tare da hanyar Wien-Bridge network (Figure 1a) wanda ke haɗa da waɗannan sashen zuwa birnin kasa. Hakan, biyu na sashen suna da tsari mai kawo da ciki baki daya suka da wasu resistors da capacitors.

Kafin ya fi sune, wani sashi ta da resistor da capacitor ake gudanar da su (R1 da C1) kuma wani mafi kyau suka da su a kan biyu (R2 da C2).

Wannan yana nuna cewa waɗannan biyu na sashen suke ci gaba da hanyar high pass filter ko low pass filter, wanda ke hada da wannan da ake bayyana a Figure 1b.

A cikin wannan zabe, a lokacin da maƙasun daɗi, yadda ake magana da capacitors C1 da C2 za a ɓace da dama saboda haka voltage V0 za a ɓace zero saboda R2 za a ɓace shorted.

Sannan, a lokacin da maƙasun kadan, yadda ake magana da capacitors C1 da C2 za a ɓace da dama.

Amma kafin ya fi sune, output voltage V0 za a ɓace zero kawai, saboda capacitor C1 za a ɓace open circuit.

Wannan abin da Wien-Bridge network ke yi a lokacin da maƙasun kadan da kuma daɗi ya ƙara shi a lead-lag circuit.

Tsarin Maƙasa ta Wien Bridge Oscillator

Amma a kan waɗannan biyu na maƙasun daɗi da kuma kadan, akwai wani maƙasa mai yawa da ake magana da ita inda irin resistance da capacitive reactance za su ɗaya daɗi, wanda ke samun output voltage mai yawa.

Wani maƙasa mai yawa na ake kira resonant frequency. Resonant frequency na Wein Bridge Oscillator ana samun tare da hanyar wannan formula:

Sannan, a lokacin da maƙasa mai yawa, phase-shift daga input zuwa output za a ɓace zero kuma yadda ake magana da output voltage za a ɓace equal to one-third of the input value. Kuma a lura, za a iya cewa Wien-Bridge za a ɓace balanced only at this particular frequency.

A cikin Wien-Bridge oscillator, Wien-Bridge network na Figure 1 za a amfani da ita a kan feedback path kamar yadda ake bayyana a Figure 2. Circuit diagram na Wein Oscillator tare da BJT (Bipolar Junction Transistor) an bayyana a nan:

A cikin oscillators, amplifier section za a haɗa da two-stage amplifier formed by the transistors, Q1 da Q2, inda output of Q2 za a fede as input to Q1 tare da Wien-Bridge network (shown within the blue enclosure in the figure).

A nan, noise inherent in the circuit za a yi ɗaukan base current of Q1 which will appear at its collector point after being amplified with a phase-shift of 180o.

Wannan za a fede as input to Q2 tare da C4 da kuma za a samun amplification additional phase-shift of 180o.

Wannan za ta ƙara net phase-difference of the signal fed back to the Wien-Bridge network to be 360o, satisfying phase-shift criterion to obtain sustained oscillations.

Amma wannan condition za a ƙara only in the case of resonant frequency, due to which the Wien-Bridge oscillators za a ƙara highly selective in terms of frequency, leading to a frequency-stabilized design.

Wien-bridge oscillators can even be designed using Op-Amps as a part of their amplifier section, as shown by Figure 3.

Amma it is to be noted that, here, the Op-Amp is required to act as a non-inverting amplifier as the Wien-Bridge network offers zero phase-shift.

Further, from the circuit, it is evident that the output voltage is fed back to both inverting and non-inverting input terminals.

At resonant frequency, the voltages applied to the inverting and non-inverting terminals will be equal and in-phase with each other.

However, even here, the voltage gain of the amplifier needs to be greater than 3 to start oscillations and equal to 3 to sustain them. In general, these kind of Op-Amp-based Wien Bridge Oscillators cannot operate above 1 MHz due to the limitations imposed on them by their open-loop gain.

Wien-Bridge networks are low frequency oscillators which are used to generate audio and sub-audio frequencies ranging between 20 Hz to 20 KHz.

Further, they provide stabilized, low distorted sinusoidal output over a wide range of frequency which can be selected using decade resistance boxes.

In addition, the oscillation frequency in this kind of circuit can be varied quite easily as it just needs variation of the