Page 191 - Op Amps Design, Applications, and Troubleshooting
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174 OSCILLATORS
Frequency
selective
circuit
FIGURE 4.1 An oscillator circuit requires amplification, frequency selection, and
positive feedback to operate.
sinewaves, the loop gain must be set to unity in order to maintain a constant-
amplitude, undistorted output signal
4.2 WIEN-BRIDGE OSCILLATOR
4.2.1 Operation
Figure 4.2 shows the schematic diagram of a Wein-bridge oscillator circuit built
around a 741 op amp. A Wien-bridge oscillator produces sinewaves and uses an
RC network as the frequency-determining portion of the circuit. The amplification
is, of course, provided by the op amp, which is essentially connected as a nonin-
verting amplifier circuit similar to those discussed in Chapter 2, The gain of the op
FIGURE 4.2 A FET-stabilized Wien-bridge oscillator circuit.
