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Friday, 15 December 2017

Hartley oscillator

Hartley oscillator

This is under the category of tuned oscillator or resonant circuit oscillator
Operation
When Vcc is applied ,the collector current begins to flow and the drop in collector voltage is coupled through capacitor C and L2 .Thus the capacitor charges to its minimum voltage ,this voltage acts as initial excitation for tank circuit ,causing a current to flow in the LC circuit  .This current induces damped harmonic oscillation across L1 and this circuit acts as input to base of transistor
This damped signal is amplified and appears at collector which is coupled as feedback to the tank circuit  C and L1. The feedback voltage across L2 is in phase with the input voltage across L1 results in sustained oscillation
The feedback voltage is in phase shift with input voltage since 180° phase shift produced by the transistor and another 180° being provided by the tank circuit
Capacitor block ,dc component of the collector circuit ,but coupled c signal
As a results of this dc is out of tank circuit this energy loss due to tank circuit  is reduced and hence the oscillation is more stable

WRITING NODE EQUATION
    Vπrπ=VπSL1+(VπVc)Sc=0
    gmVπ+VcR=VcSL2+(VcVπ)Sc=0
\end{array}\right]

= [VπVc]=0

[(1rπ+1SL1+Sc)Sc(gmSc)1R+1SL2+Sc]=0
will continue.......
MathJax example

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Hartley oscillator

Hartley oscillator This is under the category of tuned oscillator or resonant circuit oscillator Operation When Vcc is appl...