Hartley Oscillator using an Opamp

Thread Starter

burhanuddin1999

Joined Dec 22, 2020
3
I was trying to derive a model for Opamp Hartley oscillator. I used a R at mouth of opam to increase the output impedance. So i tried including it in calculation. As the opamp is modeled as output voltage of Avi so using a R in series with it with help me to reconfigure the circuit changing the circuit voltage source into a current source using source transformation theorem. Here are my calculations. Can you tell me where i messed up.

Calculation-1.jpgCalulation-2.jpgCalculation -3.jpg
 

LvW

Joined Jun 13, 2013
1,278
Sorry - but I must state that the opamp-based Hartley oscillator as shown in the linked document does not work. The circuit was derived from a transistor-based oscillator without considering the fact that the opamp is a voltage source (and not a current source). Hence, the inductor L2 acts as a pure load - and has no influence on the feedback path.
 

Thread Starter

burhanuddin1999

Joined Dec 22, 2020
3
Sorry - but I must state that the opamp-based Hartley oscillator as shown in the linked document does not work. The circuit was derived from a transistor-based oscillator without considering the fact that the opamp is a voltage source (and not a current source). Hence, the inductor L2 acts as a pure load - and has no influence on the feedback path.
Hi, Yes i am aware of the problem that's why I attached an external resistance, Ro at ouput terminal. Then by using Norton Source transformation i transformed the voltage source Avi into a current source Avi/R
 

LvW

Joined Jun 13, 2013
1,278
Hi, Yes i am aware of the problem that's why I attached an external resistance, Ro at ouput terminal. Then by using Norton Source transformation i transformed the voltage source Avi into a current source Avi/R
And what is your problem now?
I think, it would be helpful to see the circuit diagram your eqivalent small-signal diagram is based on.
 
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