Wien Bridge Oscillator

Operational Amplifiers

Published in Michael Olorunfunmi Kolawole, Electronics, 2020

The Wien bridge oscillator is a unique circuit because it generates an oscillatory output signal without having a sinusoidal input source. Instead, the amplifier supplied its own input through the two arms of the bridge, namely Z1 and Z2, as shown in Figure 4.25a, which are connected to the positive terminal to form a frequency selective feedback network. This network comprises of capacitors and resistors, as seen in Figure 4.25b and c. Instead of direct sinusoidal input source, the Wien bridge oscillator uses the capacitors in the feedback network with initial voltages to create the output. The oscillator amplifies the signal with the two negative feedback passive elements (Z3 and Z4). To analyze the circuit in Figure 4.25a, we may artificially separate the oscillating feedback network and the amplifier itself.

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Journal Information

Published in IETE Journal of Research, 2020

Ha Tran Thi Thuy, Tiep Dang Dinh, Tuan Vu Quoc, Thinh Pham Quoc, Masahiro Aoyagi, My Bui Ngoc, Van Thanh Dau, Tung Thanh Bui

The block diagram of the electronic circuit is given in Figure 9. A 170-kHz sine signal generator is connected to the excitation electrode. The sine generator circuit is a Wien bridge oscillator using an operation amplifier (TL084). The frequency of the oscillator is controlled by resistor R and capacitor C; output amplitude is adjusted by resistors R1 and R2. Because the voltage on sensing electrodes changes with their corresponding capacitance, roll and pitch angles can be monitored by measuring the amplitude of the differential voltage pair (VC1 − VC2) and (VC3 − VC4), respectively.

Wien Bridge Oscillator

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