The Hartley Oscillator- Theory and Design

Hi all,

Please verify if the circuit looks fine or not.

One thing I would like to ask is that what amplitude of oscillations is generally acceptable? I have designed oscillators with 1-2V peak magnitude and also in uV range like this one is around 90mV peak.

According to me if I manipulate RC (in BJT) or RD (in JFET) I can increase this level by increasing the gain but then again I have to adjust C or L values according to these and its not an easy task as not every time my maths works

I am not professionally designing these oscillators but just want to see the theory in action. So again what is the acceptable magnitude of oscillations? So you have any solid maths to prove why you selected RC/RD, L,C values? Any books for these?

Please give a look at the circuit. This circuit I am able to solve the parameters mathematically by solving the value of gm and then gain of multiplier is gm*RD which I make according to ratio of L2/L1. Slightly greater than that.

Thanks to all for helping and guiding me!
-Hemanshu

Higher the oscillation amplitude gives lower phase noise and better frequency stability, because the active device negative resistance or conductance reduces with increase of the oscillation amplitude.
Generally the oscillation amplitude is limited by the power supply.

Even if in your article is mentioned that to increase the efficiency of the oscillator placing its bias in class B or even C, most of the oscillators are biased in a linear class A.

@vfone

Thanks for your inputs!

High the oscillation amplitude gives low phase noise and better frequency stability, because the active device negative resistance or conductance reduces with increase of the oscillation amplitude. but it need to increase parallel resistor in tank or increase the size of transistors or increase the bias current.
The first is limited by inductors resistors and second increase the parasitic capacitance and third need to a different circuit.
Generally the oscillation amplitude is limited by the power supply.
for reach to low phase noise and better stability in frequency you can oscillator placing its bias in class B or even C, most of the oscillators are biased in a linear class A.