Hartley Oscillator using Op Amp Calculator
This Hartley oscillator circuit uses an operational amplifier (op-amp) for generating sine waves. This is a simple circuit and almost identical to the Colpitts oscillator except for differences in the tank circuit. This calculator computes the resonance frequency given the inductance of the two coils, and the capacitance value.
The main difference between Hartley and Colpitts oscillators is in their tank circuits, because the Hartley tank uses an inductive voltage divider to determine the feedback ratio, whilst Colpitts uses a capacitor voltage divider.
Since the ratio of inductances L1 and L2 determines the feedback ratio, a general rule of thumb is to make L1 factor of ten greater than L2. We also make the voltage gain of the op-amp 10 by making Rf=50 kΩ, and Rin=5 kΩ.
This is the formula for calculating the resonance frequency.
This expression describes the total inductance within the tank circuit.