Posted on Jun 10, 2012 12669
The 741 op amp integrator signal is fed into the Schmitt trigger input of an inverter. When the signal reaches the magnitude of the positive-going threshold voltage, the output of the inverter is switched to zero. The inverter output controls the FET switch directly. For a gate voltage of zero, the FET channel turns on to low resistance and the <:apacitor is discharged. The discharge current depends on the on resistance of the FET.
When the capacitor C1 is discharged to the negative-going threshold voltage level of the inverter, the inverter output is switched to Â±12 V. This switch causes the FET channel to be switched off, and the discharging process is switched into a charging process again. Using the components shown, an output frequency of about 10kHz with 0.1 % linearity can be obtained.