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I am learning about LC circuits. I tried to build one by myself. The schematic is in the picture below.

When I turn on the power, I can't get any AC output from R1 on multimeter, but I can get some DC voltage.

Because the frequency in this circuit should be around 10kHz, I connected R1 to a power amplifier, and I can't hear any sound.

Does anyone know why it is not working or if it is working and just I used the wrong way to measure it?

lc circuit

JRE
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sa as
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  • What multimeter are you using? Most (especially inexpensive ones) can only measure line frequency AC (50 or 60 hertz, maybe a little higher.) Those wouldn't be able to detect your oscillator output even if the oscillator is working. – JRE May 09 '20 at 11:17
  • the multimeter i am using is about 13 dollars.I'll check user manual late to see how much frequrncy it can be measure.and thank you for corrected my syntax error. – sa as May 09 '20 at 11:28
  • Maybe post the meter model and a link to the handbook. – JRE May 09 '20 at 12:22

1 Answers1

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I can say with absolute certainty that you have ruined the transistor biasing by not having a capacitor fitted as shown below: -

enter image description here

Without the capacitor shown above, the DC voltage at the base will be about 3.7 mV and this stops it working dead.

And, I can see that it is intended to operate at 10 kHz but, even with the capacitor in place, it might still not work if you have used crappy electrolytic capacitors. Other than that, it's really hard to make this very simple common-collector Colpitts oscillator not work.

This answer provided to you on your previous question shows the role of the capacitor I have added to your circuit: -

enter image description here

Notice the phrase "DC block"?

Andy aka
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