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  • DC 5 V for input

  • Three 10 nF capacitors

  • One 2.2k resistor

  • One 680k resistor

  • Two 5.6k resistors

My assignment is to make an oscillator using only the elements given above.

This is the desired output waveform.

enter image description here

This is the circuit I have tried so far. Please tell me what is wrong and how can I make a circuit with such a waveform.

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    \$\begingroup\$ Q1 is not properly biased. And have a look at this question, it might help. \$\endgroup\$ Sep 28, 2022 at 11:42

1 Answer 1

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Please tell me what is wrong and how can I make a circuit with such a waveform.

In your diagram you had base connected to +5 volts and that would have destroyed the BJT.

However, given the component choices you are presented with, this circuit seems to be the most likely one to work. It uses the 680 kΩ to self bias the BJT and will simultaneously present a low-ish impedance to C2 to create enough phase shift to cause oscillation: -

enter image description here

Yup, looks like it'll work: -

enter image description here enter image description here

It oscillates at a shade under 1 kHz.

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  • \$\begingroup\$ I'm Korean, so I'm not very good at expressing my gratitude, I really want to thank you for your help. Have a nice day :) \$\endgroup\$
    – Yooseong
    Sep 28, 2022 at 13:16
  • \$\begingroup\$ @Yooseong -- Here is a Falstad version for you to try, and you can even click the "Play Sound" button to hear the resulting waveform, which registers at about 939.22 Hz using the free Phyphox Android app and Falstad on Chrome on split screen. \$\endgroup\$ Mar 26 at 1:18
  • \$\begingroup\$ Why would anyone use foolstad when they are clearly using a decent simulator (look at their question) and not a green confusing toy. \$\endgroup\$
    – Andy aka
    Mar 26 at 8:58
  • \$\begingroup\$ Thank you for your honest and good feedback. I have been using LTSpice for years and wanted another one to use, and an online simulator would have been nice. Falstad has indeed been confusing, since results have been different from LTSpice. I'm going to stop using Falstad. Thanks again. \$\endgroup\$ Apr 11 at 5:16

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