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Hartley Oscillator Simulation

Electrical Engineering Asked on December 31, 2021

Hello i want to simulate the following Hartley Oscillator that i designed on LTspice
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But when i run it i am not getting the sine output. Where is the issue? How can i get a correct output?

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UPDATE circuit after suggested changes
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2 Answers

The resonant frequency of 10pF and 0.1 henry is

Fres = 1/(2 * PI * sqrt (L * C)) = 0.159/sqrt(0.1 * 10e-12)

Fres = 0.159 / sqrt(1e-12) = 0.159 * 1,000,000 = 159,000 Hertz.

Does the opamp have much usable gain, at 160KHz?

Answered by analogsystemsrf on December 31, 2021

Your 384 ohm resistor is in the wrong place: -

enter image description here

You may also need to lower R1 to allow the circuit to initiate and sustain oscillations.

The OP-07 is going to struggle with the operating frequency - try making C1 ten to one hundred times higher initially.

Don't be too surprised if sine purity isn't outstanding.

Here's a simulation result: -

enter image description here

Because the OP-07 is a bit crappy on bandwidth, I increased the capacitor from 4.4 pf to 4.4 nF to lower the oscillation frequency 30 odd times, left R1 at 100 kohm (so it didn't load the output too much) and made the feedback resistor 1 Mohm: -

enter image description here

Sometimes you have to experiment with values. You can get oscillation higher frequencies if you lower the inductance values by 100:1 and the sine-wave purity is much better.

Answered by Andy aka on December 31, 2021

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