Which is a rather misleading description for a circuit not oscillating at all, isn't it?In this case the output was not even closer to sinusoidal.
Maybe you are not setting up the simulation correct in LT Spice.
I don't have your transistor model in LT, but it works with gen purpose 2N3904.
Waveforms were sampled on the emitter.
Next set shows the results with the buffer added.
10 ohm is realistic for industry standard 10 MHz, HC49 case, AT-cut. Miniaturized cyrstals have probably higher Rs.Also R4 value should be 4 ohm for Q around 800 K.
It will be SC cut, 800K min Q, Co=4.3pF,C1=5.5fF, R1=10 ohm max. according to the datasheet. Since freq will be 10 Mhz, I calculated L as 47 mH. To satisfy Q value R must be around 4 ohm10 ohm is realistic for industry standard 10 MHz, HC49 case, AT-cut. Miniaturized cyrstals have probably higher Rs.
thank you so much for your interest! I tried the circuit with 2N3904, and it seems working. However, I couldnt get pure sinusoidal and the FFT didnt seem promising.
In the first picture, oscillation didnt seem to be symmetrical with regard to the dc line. Does it mean that transistor is saturated? Or is it the nature of normal oscillation.
Now Iam working with differential amplifier part. However, It is difficult for me to determine capacitor and resistor values. What values I should use for bypass capacitor connecting my output of colpitts and input of amp for 10 Mhz? Capacitor must be like a short circuit at 10 Mhz. What should I use for c1 and other resistors?
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