Electrical Engineering Asked on December 31, 2021
Hello i want to simulate the following Hartley Oscillator that i designed on LTspice
But when i run it i am not getting the sine output. Where is the issue? How can i get a correct output?
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: -
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: -
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: -
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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