The 741 operational amplifier act as a voltage follower and its non inverting input is connected to the variable resistor. The output line almost requires a 12/24 volts DC motor.

• 1x tip3055 npn power transistor
• 1x mje34 pnp power transistor
• 3x 1kohm 1/4w resistor
• 2x 25kohm 1/4w variable resistor
• 2x 1500uf 16v capacitor
• 1x 741 operational amplifier