stenzer
Advanced Member level 3
Hi,
I "designed" a collpits oscillator in base configuration according to a textbook [1] depicted in Fig. (Bild) 1a (it's in german, sorry ;-)). My design/siumulation does not use a quartz crystal.
I simulated the oscillator in LTspice with a PMBT2222A [2] NPN BJT from Nexperia. I set the emitter resistance R_E to 20k, and the circuit operates fine. The change of R_E leads to a loop gain (Vs in the textbook) of about 10, and a quality factor of the whole circuitry Q_B of about 66.
Concerning the loop gain of about 10, which is significantly larger than 1, the circuitry should certainly start oscillating.
My question is, is there an analytical way to determine the stability in any way? Further, is there a way to determine the turn-on time, which the oscillator needs until reaching steady state? The analysis should preferable include the correct transistor, if possible.
I'm also curious about the graph in the right of Fig. (Bild) 2 in [1], where the hatched region is "The area in which experience has shown that optimum quality values can be achieved for the coil and the oscillating circuit (no-load quality)". Where do I get such an information, except from this textbook?
[1] https://books.google.at/books?id=u0spBAAAQBAJ&pg=PA211&lpg=PA211&dq=colpitts+oszillator+b%C3%B6hmer&source=bl&ots=g2XQJI-cW1&sig=ACfU3U1Hn5TNH0mKV-19EkzMq9g8Y8N0eA&hl=de&sa=X&ved=2ahUKEwiOpevd9bDoAhVNa8AKHVVTCAoQ6AEwA3oECAoQAQ#v=onepage&q=colpitts%20oszillator%20b%C3%B6hmer&f=false
[2] **broken link removed**
BR
stenzer
I "designed" a collpits oscillator in base configuration according to a textbook [1] depicted in Fig. (Bild) 1a (it's in german, sorry ;-)). My design/siumulation does not use a quartz crystal.
I simulated the oscillator in LTspice with a PMBT2222A [2] NPN BJT from Nexperia. I set the emitter resistance R_E to 20k, and the circuit operates fine. The change of R_E leads to a loop gain (Vs in the textbook) of about 10, and a quality factor of the whole circuitry Q_B of about 66.
Concerning the loop gain of about 10, which is significantly larger than 1, the circuitry should certainly start oscillating.
My question is, is there an analytical way to determine the stability in any way? Further, is there a way to determine the turn-on time, which the oscillator needs until reaching steady state? The analysis should preferable include the correct transistor, if possible.
I'm also curious about the graph in the right of Fig. (Bild) 2 in [1], where the hatched region is "The area in which experience has shown that optimum quality values can be achieved for the coil and the oscillating circuit (no-load quality)". Where do I get such an information, except from this textbook?
[1] https://books.google.at/books?id=u0spBAAAQBAJ&pg=PA211&lpg=PA211&dq=colpitts+oszillator+b%C3%B6hmer&source=bl&ots=g2XQJI-cW1&sig=ACfU3U1Hn5TNH0mKV-19EkzMq9g8Y8N0eA&hl=de&sa=X&ved=2ahUKEwiOpevd9bDoAhVNa8AKHVVTCAoQ6AEwA3oECAoQAQ#v=onepage&q=colpitts%20oszillator%20b%C3%B6hmer&f=false
[2] **broken link removed**
BR
stenzer