Negative resistance oscillator.

146

01:57:34

The tank losses in the form of leakage resistances are causing the oscillations to damp down.

So, the effective parallel leakage resistance can be cancelled by putting the same magnitude negative resistance in parallel.

After doing this we get undamped or sustained oscillations at tank's resonant frequency.

Resistance in parallel at resonance is 

Rp = -(1+Q^2)×Rs;
Where Q is the quality factor of the tank.

With the component values used in schematics:

Rp ~ -Q^2× Rs
      ~ -100^2×10m

Rp = -100 ohm.

Toggle the switches in the below order to see the operation. ( switches are named from left to right in schematic. )

SWITCH2 : CLOSE; to charge the capacitor with 1V supply.

SWITCH2: OPEN.

SWITCH1 : CLOSE; to see the DAMPING(dying) sinusoidal oscillations from LC tank.

SWITCH3 : CLOSE; to see that there is NO DAMPING, i.e. SUSTAINED oscillations.
Which is due to -ve resistance offered by OPAMP circuit.

published 2 years ago

dragoola

2 years ago

you do know you just need a coil and capacitor at the same values in series and just pules it with a PWM at is resonant frequency witch depends on the values and you can get 40v and 40 amps if you are pulsing in with 9Vs. but you know that already right?

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