This circuit is from an old Popular Electronics, but it can be easily implemented nowadays, even adapted to act as a shield. The circuit has the frequency given by C1 and adjusted in R1.
Other operational amplifiers can be used on this unit gain amplifier. The circuit is from the 1993...
Based on components from Linear Technology, we find this circuit in a 2005 manual. The circuit...
DC motors from 6 to 12 volts and currents up to 2 amps can be controlled with this circuit. The TIP41...