the hartley oscillator is the dual of the colpitts oscillator which uses a voltage divider made of two capacitors rather than two inductors. although there is no requirement for there to be mutual coupling between the two coil segments, the circuit is usually implemented using a tapped coil, with the feedback taken from the tap, as shown here. the optimal tapping point (or ratio of coil inductances) depends on the amplifying device used, which may be a bipolar junction transistor, fet, triode, or amplifier of almost any type (non-inverting in this case, although variations of the circuit with an earthed centre-point and feedback from an inverting amplifier or the collector/drain of a transistor are also common), but a junction fet (shown) or triode is often employed as a good degree of amplitude stability (and thus distortion reduction) can be achieved with a simple grid leak resistor-capacitor combination in series with the gate or grid (see the scott circuit below) thanks to diode conduction on signal peaks building up enough negative bias to limit amplification.