| Electronics > Beginners |
| Need help getting 2.4MHz piezo to oscillate at its resonate frequency |
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| MatCat:
I am trying to create a 2.4MHz oscillator which would output a square wave good enough to drive a fet or power transistor, I found the following circuit in my googling which does oscillate (I changed the values to get close to my 2.4MHz), I am running it with a 12V supply and getting a 4.2V peak to peak at my desired frequency, however its riding on an 8V DC bias! I tried going through a cap to block the DC which does give me the desired waveform but of course half of it then dips below ground, I tried using a diode to block the negative going transition but it doesn't appear to work at all! Original Circuit Output of oscillator Output through cap and diode |
| T3sl4co1l:
You need a DC restorer. What are you actually using the 2.4MHz for? Tim |
| MatCat:
--- Quote from: T3sl4co1l on October 26, 2018, 12:33:19 am ---You need a DC restorer. What are you actually using the 2.4MHz for? Tim --- End quote --- I want to use it to drive a power transistor to drive a piezo (humidifier) |
| spec:
+ MatCat Your best bet, by far, is to use an integrating oscillator made from a Schmidt trigger. The Schmidt trigger could be a Schmidt trigger logic chip (74HC14 or 74HC132), or a Schmidt trigger made from a comparator chip The output from the above circuits would drive the gate of a power MOSFET nicely. |
| IanMacdonald:
Look up the Hartley and Colpitts oscillators. These are two well tested arrangements that work reliably. In the circuit you show I think the 10k will be far too low, and will be near-saturating the transistor. Try maybe 47k. |
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