I really appreciate you high quality content. great if you make also videos for RF and/or modulation and demodulation topologies in LTSpice. VCO and control loops, even Filters. maybe too much.
I am learning how to build a colpitz oscilator in the range of GHz. Your video helped me so much. I have 2 questions. 1. where would I measure if I want to see the input oscilation ? so that I have both input and output sine-waves crossing each other. 2. I tried lowering the L C in the colpits tank, so that I get a higher frequency, but it starts failing to oscilates, any idea how I can make it reach above 1 GHz? Thank you so much
1. In this case, you don't exactly have a sinewave of, i don't know, 100mV peak to peak and then amplified. It's a closed loop system, so, the intrinsic noise of the circuits gets amplified by the barkausen condition to keep the instability "stable". In the node of the base of the transistor, you have just the same waveform but with/withouth the dc component, and that's it. Correct me if I am mistaken 2. Only lowering will not work. Lower capacitors like in the range of 1pF, 10pF or even lower like 100fF, hardly will work as capacitor, because the parasitic will get in the way and will prevail in that range of value. Think about having a Capacitor C1 with 1n, 1mOhm and 100pH of ESR and ESL, and then put a 100fF capacitor with 100pH or 1nH of ESL and 1mOhm of ESR. As I said in the video, when choosing a capacitor, always look at the "Impedeance vs Frequqency" graph. The curve will look like a V, which the bottom point is called SRF Self Resonant Frequency, given by the classical formula f=1/sqrt(ESL*C). If you put a 100fF, always look that HE will be a capacitor at 1GHz. That's the challenge. If you can't, you probably have to design a colptiz with other methods or to choose high costly capacitor Hope that it helped
Some tips. Reduce stray capacitances, lead inductance, reactive loading by probes. proper ac ground with multiple good quality caps Feedback attenuator C1, C2 close to 2. Operate the transistors at low voltage but high current for highest transconductance. Choice of transistors is also important, some were designed for audio(BC series), switching, high voltage etc. A great clue of HF capabilities is the max. operating voltage Vce < 20 V
Thanks for the videos.... I just wanted to know where they got the values ?how do you calculate them? .... because I tried to simulate this value with another transistor and it didn't work
As shown in the video, you Will have to provide transistors with good bandwith Bf, or else It won't work For the formula, you can search up any application note to design the LLC colpits tank resonator, they are very simple
I really appreciate you high quality content. great if you make also videos for RF and/or modulation and demodulation topologies in LTSpice. VCO and control loops, even Filters. maybe too much.
Hi Mano Arrostita, great video. Do you have also spectrum analyzer to show more about the rf electronics? Thank you :)
In the Company yes, at home, unfortunately no. I only have the built-in spectrum of the oscilloscope xD
I am learning how to build a colpitz oscilator in the range of GHz. Your video helped me so much. I have 2 questions.
1. where would I measure if I want to see the input oscilation ? so that I have both input and output sine-waves crossing each other.
2. I tried lowering the L C in the colpits tank, so that I get a higher frequency, but it starts failing to oscilates, any idea how I can make it reach above 1 GHz?
Thank you so much
1. In this case, you don't exactly have a sinewave of, i don't know, 100mV peak to peak and then amplified. It's a closed loop system, so, the intrinsic noise of the circuits gets amplified by the barkausen condition to keep the instability "stable". In the node of the base of the transistor, you have just the same waveform but with/withouth the dc component, and that's it. Correct me if I am mistaken
2. Only lowering will not work. Lower capacitors like in the range of 1pF, 10pF or even lower like 100fF, hardly will work as capacitor, because the parasitic will get in the way and will prevail in that range of value. Think about having a Capacitor C1 with 1n, 1mOhm and 100pH of ESR and ESL, and then put a 100fF capacitor with 100pH or 1nH of ESL and 1mOhm of ESR.
As I said in the video, when choosing a capacitor, always look at the "Impedeance vs Frequqency" graph. The curve will look like a V, which the bottom point is called SRF Self Resonant Frequency, given by the classical formula f=1/sqrt(ESL*C). If you put a 100fF, always look that HE will be a capacitor at 1GHz. That's the challenge. If you can't, you probably have to design a colptiz with other methods or to choose high costly capacitor
Hope that it helped
Some tips.
Reduce stray capacitances, lead inductance, reactive loading by probes. proper ac ground with multiple good quality caps Feedback attenuator C1, C2 close to 2.
Operate the transistors at low voltage but high current for highest transconductance. Choice of transistors is also important, some were designed for audio(BC series), switching, high voltage etc. A great clue of HF capabilities is the max. operating voltage Vce < 20 V
Thanks for the videos.... I just wanted to know where they got the values ?how do you calculate them? .... because I tried to simulate this value with another transistor and it didn't work
As shown in the video, you Will have to provide transistors with good bandwith Bf, or else It won't work
For the formula, you can search up any application note to design the LLC colpits tank resonator, they are very simple
I'm not talking about the formula of colpits tank but about DC block, dc bias, R4, R3, C4 .... how did they calculate these values?@@manoA98A
I'm not talking about the formula of colpits tank but about DC block, dc bias, R4, R3, C4 .... how did they calculate these values?@@manoA98A