Wien Bridge Oscillator
Wien Bridge Oscillator-The Wien- ground oscillator is the standard oscillator circuit for all frequentness in the range of 10 Hz to about 1 MHz.
It's the most constantly used type of audio oscillator as the affair is free from
circuit oscillations and ambient temperature.Fig-1 shows the circuit of Wien ground oscillator.
It's basically a two- stage amplifier with R-C ground circuit. The ground circuit has the arms R1C1,.
R3, R2C2 and tungsten beacon Lp. Resistances R3 and Lp are use to stabilise the breadth of the
The transistor T1 serves as an oscillator and amplifier while the other transistor T2 serves as
an inverter ( i.e. to produce a phase shift of 180º).
The circuit uses positive and negative feedbacks.
The positive feedback is through R1C1, C2R2 to the transistor T1.
The negative feedback is through
the voltage separator to the input of transistor T2.
The frequence of oscillations is determine by the
series element R1C1 and resemblant element R2C2 of the ground.
When the circuit is start, ground circuit produces oscillations of frequence determined by exp.
(i). The two transistors produce a total phase shift of 360º so that proper positive feedback is assured.
The negative feedback in the circuit ensures constant affair. This is achieved by the temperature
sensitive tungsten beacon Lp. Its resistance increases with current. Should the breadth of affair tend
to increase, more current would give further negative feedback. The result is that the affair would
return to original value. A rear action would take place if the affair tends to drop.
(i) It gives constant affair.
( ii) The circuit works relatively fluently.
(iii) The overall gain is high because of two transistors.
(iv) The frequence of oscillations can be fluently change by using a potentiometer.
( i) The circuit requires two transistors and a large number of factors.
(ii) It can not induce veritably high frequentness.
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