Page 226 - Op Amps Design, Applications, and Troubleshooting

208 OSCILLATORS

FIGURE 4.12 A triangle-wave
oscillator designed for a 1.5-kilohertz
operating frequency.

FIGURE 4.13 Oscilloscope displays showing the actual performance of the triangle-wave oscilla-
tor shown in Figure 4.12. (Test equipment courtesy of Hewlett-Packard Company.)

TABLE 4.3

Design Goal Measured Value
Frequency 1.5 kilohertz 1.59 kilohertz
Ramp amplitude ±3 volts +3.2 volts, -3.3 volts

circuit. An interesting modification to the circuit involves paralleling RI with a
smaller resistor in series with a diode. This will cause one alternation to be signif-
icantly shorter and will generate a forward or reverse sawtooth waveform (deter-
mined by me polarity of the added diode). The slew rate of the op amp ultimately
limits the minimum ramp time.