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Basically you use current sources to charge and discharge a capacitor. An oscillator can drive the selection of in and out current sources or you can use two comparators to switch when the capacitor reaches your desired voltage at each end of the swing.
If you do not want extreme linearity and the voltage swing is much less than your power supply levels, resistors to the two power supply rails will work.
If you want better performance use current sources made from discrete transistors or op amps.