Demonstration and Discussion of Colpitts Oscillator (8 - Oscillators)
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- Опубліковано 10 бер 2023
- Let's build and test a Colpitts Oscillator in the lab. We'll change various components and see how they affect the waveform on the oscilloscope.
Aaron Danner is a professor in the Department of Electrical and Computer Engineering at the National University of Singapore.
danner.group
Video filmed and edited by Cheryl Lim.
@randomcheryl
When I designed vhf and uhf oscillators for the TV industry we almost exclusively used a common base configuration.alternatively we used common collector. The tuning was accomplished with either switching in various inductors or alternatively a variable capacitor across the inductor. Just FYI.
Excellent demonstration! Thanks. Subbed and rang the bell.
Awesome, thank you!
Aaron, your videos are great!!
Your contents deserve many more subscribers!!
Thank you very much!!
this is extremely true helps me a lot for my projects and learning
Great video with great explanation.
Great video.
Thanks 🙏
Very nice. Became ur subscriber ! ❤🎉
Aaron,
Can you please upload videos about analog mixers?
Balanced, double balanced
I really like your videos it helps me a lot
I got this circuit to run in LTSpice (schem at 3:40). Paste below (the netlist) in a spice directive window I changed gain from -2 to -1.25 to reduce the current spike when the collector becomes forward biased (RE2 from 1k to 4k) (gain limiting mechanism?) but it takes 10mSec to start. run and select "pick visible traces" button in the toolbar.
RBtop 9V base 12k
R2 base 0 8.2k
V1 9V 0 9
C1 col 0 1n
L1 col tnk_out 47µ
Q1 col base emit 0 2N2222
C2 tnk_out 0 1n
RE1 emit 0 1k
RE2 N001 0 4k
RL 9V col 1k
C4 emit N001 10n
C3 tnk_out base 82n
.model NPN NPN
.model PNP PNP
;op
.tran 0 14m 13.99m
.meas TRAN vout PP v(col)
.meas TRAN vin PP v(base)
.meas TRAN vout2 PP v(emit)
.meas TRAN ie PP ie(q1)
.model 2N2222 NPN(IS=1E-14 VAF=100 BF=200 IKF=0.3 XTB=1.5 BR=3 CJC=8E-12 CJE=25E-12 TR=100E-9 TF=400E-12 ITF=1 VTF=2 XTF=3 RB=10 RC=.3 RE=.2 Vceo=30 Icrating=800m mfg=NXP)
.backanno
.end
.backanno
.end
Hi professor. Great Video! You are helping me remember stuff I did not use since college.
Can anyone also help me out?
On the previous video, we saw that we don't want any current leaking from the tank circuit to the amplifier (4:06 of the last video (7 - Oscillators) ), therefore the input impedance of the circuit should be way higher than the impedance of the components in the tank circuit.
The impedance of the 1nf capacitor at 1Mhz is 1K ohm. And the input impedance of the amplifier circuit should be close to (12K || 8.2K) ~ 5K ohm.
As a engineer who has no practical experience in analog design I was wondering what are reasonable numbers for this. The input impedance being only 5x the impedance of the last 1nF capacitor seems low for me, since this would mean around 20% of the current will go to the amplifier and the approximation that was performed at 4:06 of the last video (7 - Oscillators) might not be that valid. Is a good enough approximation? Are there any rule of thumbs for this?
Thanks
Excellent demonstration !
how to follow your videos ?
thanks for the video ....but why did you choose c1 and c2, because I looked at the data sheet of the transistor and saw 8 pF with emitter capacitance and I wonder why you chose up to 1 nF. So how do we know which values should you select?
Hello! Good video! As I understand - the quality factor must be as more as possible. So we can`t load LC circuit: as a result we can have high impedance on input. BJT have low input impedance (emitter resistor can increase Rin, but there is the Miller effect and on high frequency input impedance becomes lower that on DC). An RF MOSFET BF998 can be a good variant. Am I right?
Hmm, this works well in simulation but I've spent now a couple days trying to get it to work in real life. I even tried changing the values in case for some reason my components were not suitable to such a high frequency range. Using all 10uF caps and 47mH inductor should give a frequency of about 325 Hz, but even that was a complete failure for me. Just cannot get this to work under any circumstances. Any advice?
Sir,
Pls show a Colpitt's oscillator with the help of a crystall and transistor.
Thanks 😁
How to calculate the resistors value and capacitors value? I mean how do you consider those values 12k , 1k,8.2k, 82nf?
Hope you will respond to my question!!
We will have a new set of videos ready soon for designing transistor amplifiers.
A beautiful sine wave does not have flat bottom...