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Electronics ain't easy
United States
Приєднався 29 січ 2022
I make videos about electronics. Mostly electronic circuits. I explain why they work.
JFET as a Voltage Controlled Resistor --- Voltage Controlled Variable Gain Amplifier
In this vid, I explained how a JFET can be used as a voltage controlled resistor when the voltage is kept low (under 100mV).
Then, I show how a JFET can be used as a variable resistor in a inverting op-ampl amplifier making the amplifier voltage controlled (thanks to the variable gain offered by the JFET used as a voltage controlled resistor).
Not super practical but interesting nonetheless.
Links to LTSpice simulation files:
drive.google.com/file/d/1AF85w0IjEdGOHN5xjtMOpITbyv0PF8CR/view?usp=sharing
drive.google.com/file/d/154sTbNG43NuM0YGukoLBm7ZswhZQp5ek/view?usp=sharing
Then, I show how a JFET can be used as a variable resistor in a inverting op-ampl amplifier making the amplifier voltage controlled (thanks to the variable gain offered by the JFET used as a voltage controlled resistor).
Not super practical but interesting nonetheless.
Links to LTSpice simulation files:
drive.google.com/file/d/1AF85w0IjEdGOHN5xjtMOpITbyv0PF8CR/view?usp=sharing
drive.google.com/file/d/154sTbNG43NuM0YGukoLBm7ZswhZQp5ek/view?usp=sharing
Переглядів: 77
Відео
Sallen-Key 2nd order (2 pole) active low pass filter --- LTSpice simulation (AC analysis bode plot)
Переглядів 14921 день тому
In this video, we study the Sallen-Key active low pass filter. In particular, we generate the Bode plot to see the filter's response as the input frequency increases. The Sallen-Key filter is actually 2 low pass passive RC filters combined into one, hence, the 2 poles and the 2nd order (40dB/decade slope). We try to answer the following questions: Why is there a positive feedback loop? Why is t...
RC low pass filter explained with LTSpice
Переглядів 7421 день тому
In this video, I go over the RC low pass filter and explain what it does using LTSpice simulations. Links to the LTSpice simulation files: 1) drive.google.com/file/d/1kTj8i-7yhUu5FPZY-U8zlyAGTl35iCRV/view?usp=sharing 2) drive.google.com/file/d/1K0pJtVZPT_t5x2rgHFwCkbC-zGCEkIeO/view?usp=sharing 3) drive.google.com/file/d/1RI_69ivKA621h_wcA4LWJXseB1OGnI3N/view?usp=sharing
Pulse Induction Metal Detectors. How do they work? Part 5: Audio stage. LTspice analysis.
Переглядів 183Місяць тому
In this video, I explain how the DC output voltage coming from the sampling integrator is used to modify the loudness of a fixed frequency audio tone. Here, we are using loudness of a fixed frequency signal to signal the presence of a metal target under the coil. Another option is to use the DC output voltage coming from the sampling integrator to pitch up the frequency of an audio signal when ...
Pulse Induction Metal Detectors. How do they work? Part 4: Final gain stage. LTspice analysis.
Переглядів 322Місяць тому
In this 4th installment of my simulation series about pulse induction metal detectors, I am talking about the final gain stage right after the samping integrator stage. Now, the interesting part is the threshold which controls whether the signal from the sampling integrator gets amplified or "nullified". In real life, the metal detectorist would turn his/her metal detector and adjust the thresh...
Pulse Induction Metal Detectors. How do they work? Part 3: Sampling integrator. LTspice analysis.
Переглядів 448Місяць тому
In this third installment, I go over the integrator that is used to generate a signal that indicates the presence of metal under the coil, assuming that the coil is in movement. The role of the integrator is to take those samples coming from the flyback decay and generate a dc level (I should say, near DC) that is low when the coil is stationary (even if over a target) but high if moving over a...
Pulse Induction Metal Detectors. How do they work? Part 2: Front end (preamp). LTspice analysis.
Переглядів 182Місяць тому
This is part 2 of my series of videos about how pulse induction metal detector work. Here, I am concentrating on the frontend which includes the transmit circuit (kinda already described in part 1 and the preamp). I highly recommend the book "Inside the Metal Detector" by Overton and Moreland if you want to know more about metal detectors work. Link to LTspice simulation file: drive.google.com/...
Pulse Induction Metal Detectors. How do they work? Part1: Transmit circuit. LTspice analysis.
Переглядів 2942 місяці тому
This is the first video in a series that I plan to make about pulse induction metal detectors. I plan to use LTspice to simulate all the (basic) steps/modules needed to detect metals with a PI metal detector. I think it's a great way to learn about transistors (used as switches) and op-amps (used as small signal amplifiers, differential amplifiers, integrators, etc). Here, I am showing how a pu...
op-amp integrator
Переглядів 1 тис.4 місяці тому
The op-amp will modify its output so that the voltage at its 2 inputs are the same. In our case, the op amp must make sure the inverting input is at virtual ground since the non-inverting input is grounded. This means the op amp output voltage will be such that the current in the input resistor and capacitor is constant. For that to happen, the voltage across the capacitor must rise (linearly),...
AC load line for BJT common emitter amplifier
Переглядів 2355 місяців тому
In this video, I explain how to plot the dc load line and the ac load line for a common emitter amplifier with capacitively coupled output. How to get the 2 points to draw the ac load line is not particularly obvious and it's rather hard to explain tbh. Tried my best though. The common emitter amplifier has 2 resistors on the emitter lead for stability, one is being bypassed by a capacitor.
Cheap regulated power supply from amazon/ebay based on the LM317
Переглядів 1596 місяців тому
In this video, I show the instructions manual (2 pages actually) and explain what this little regulated power supply kit does. It's more than a regulated power supply since it's also a square wave generator (RC oscillator), a logic pen with either LED or buzzer output. Watch out as mine didn't have all the connections for the buzzer circuit. Easy fix though.
Detailed explanation for RC oscillator using NOT logic gates
Переглядів 2186 місяців тому
In this video, I explain in detail how astable multivibrator aka RC oscillator aka square wave generator works in the context of CMOS logica gates, here, NOT aka INVERTER gates like the CD4069. The big issue is how the capacitor charges and discharges. I am trying to explain how it works but, as I often say, it ain't easy. In the vid, I say that the switch occurs when input goes from 0V to 5V b...
Thevenin theorem (equivalent circuit). Very simple example.
Переглядів 115Рік тому
In this previous video about the astable multivibrator using an op-amp: ua-cam.com/video/yKleMEaHm_k/v-deo.html I kinda went right over something rather interesting: figuring out what the voltage is 1 of the 2 inputs of the op-amp depending on the output value of the op-amp. In this present video, I go over in great details how you can compute that voltage using the Thevenin theorem and get exa...
Op-amps still! Astable multivibrator (oscillator). Learn electronics with Radioshack.
Переглядів 269Рік тому
Another experiment from the "130 in 1 Electronic Project Lab" from Radioshack. This time, it's experiment 89: "Operational Amplifier Winking Led". Nothing more than a comparator with a slightly shifting reference voltage at the positive input and a capacitor charging and discharging at the negative input. Output is a nice square wave.
Op amp used as Schmitt trigger. Learn electronics with Radioshack.
Переглядів 587Рік тому
In this video, I explain experiment 74 (Schmitt trigger circuit) of the Radioshack "130 in 1 electronic project lab". Comparator circuit, op-amp, positive feedback loop, hysteresis, etc.
Op amps! Non-inverting single-power supply audio amplifier. Radioshack 130 in 1 project lab.
Переглядів 187Рік тому
Op amps! Non-inverting single-power supply audio amplifier. Radioshack 130 in 1 project lab.
More op-amps! Radioshack's "Inverting two-power supply amplifier"
Переглядів 65Рік тому
More op-amps! Radioshack's "Inverting two-power supply amplifier"
Radioshack's "Non-inverting two-power supply amplifier". Op-amp audio amplifier.
Переглядів 285Рік тому
Radioshack's "Non-inverting two-power supply amplifier". Op-amp audio amplifier.
DC voltage amplification with op amp. Learn electronics with Radioshack!
Переглядів 595Рік тому
DC voltage amplification with op amp. Learn electronics with Radioshack!
Op amps! Let's check out the "comparator" circuit in Radioshack electronics lab!
Переглядів 178Рік тому
Op amps! Let's check out the "comparator" circuit in Radioshack electronics lab!
Learn electronics with Radioshack: light dimmer
Переглядів 176Рік тому
Learn electronics with Radioshack: light dimmer
Transformer-type, one-stage and two-stage phase splitters for push-pull tube amp
Переглядів 265Рік тому
Transformer-type, one-stage and two-stage phase splitters for push-pull tube amp
Push-pull amplifier explained (in details)
Переглядів 1,3 тис.Рік тому
Push-pull amplifier explained (in details)
Negative feedback loop in the Fender Champ 5F1
Переглядів 547Рік тому
Negative feedback loop in the Fender Champ 5F1
Impedance matching and why an output transformer is needed in tube amps
Переглядів 362Рік тому
Impedance matching and why an output transformer is needed in tube amps
Triode operation under fixed bias and cathode bias
Переглядів 183Рік тому
Triode operation under fixed bias and cathode bias
Hartley oscillator using 1 transistor (class C amplifier). How are the oscillations maintained?
Переглядів 504Рік тому
Hartley oscillator using 1 transistor (class C amplifier). How are the oscillations maintained?
From electret condenser mic to audio Vu-Meter using LM386 pre-amp and dual LM741 peak detector
Переглядів 243Рік тому
From electret condenser mic to audio Vu-Meter using LM386 pre-amp and dual LM741 peak detector
Can we use mosfet instead as it's hard to find jfet nowadays? Great video.
You probably can but, tbh, i have only seen jfets used as VCR.
You're missing the cool model: series resistance and parallel capacitance for the coil. When you use spice you'll want to model all parts like they are in real life. Great work. I have wanted to work on this myself
I'm an EE and also gold prospect. I'd love to work on this with you. You could solve for the critical damping in the 2nd order laplace. If you're willing to collaborate on this I'd love to. I'm a circuit designer and PCB for 20+ years.
I like the consent immensely, but I find I need to pause and reverse engineer some of the mathematics, as you don't really let us know where you are going with it. It would be nice to have a little more of the algebraic steps shown so that we can concentrate on transistor theory rather than the algebra. Still... great content thanks.
instantaneous thumbs down.. hideous explanation.. please stay far away from anything having to do with education sir
Спасибо вам большое, за ваши замечательные обьяснения этой ламповой схемы!!! Я как раз недавно собрал этот усилитель 5f1 из доступных мне компонентов. Конечно его еще нужно улучшать))) Ваши видео очень помогают понять эту тему!!! Спасибо! 😃👍
This is fantastic stuff. I like your style 👍🏻
This video was really helpful. Thank you!
Thank you kind sir
I have a 3 lead electret element that I want to use with a phantom power audio interface. I simply used the center lead on the element to positive, and one of the casing leads to the negative, then plugged the cable into the audio interface? I'm not hearing anything when I did this...what am I doing wrong? Thanks!
Should get larger white board.
Good explanation
Thanks :D
Nice that you are back.
I have 2 questions. FIRST.. I saw that usually C1 and C2 capacitors are electrolitics. Lets take capacitor C1. Plate A is positive and plate B is negative. It is possible to charge C1 in reverse connection (plate A on ground and plate B to positive plate of supply)? Because at one moment Plate A has zero potential and plate B has -5.4 potential. When Q1 is conducting Plate A is on the ground and Plate B is on positive side of supply. I understand that this is the phase of discharge of C1 (i saw that a charged capacitor in reverse connection discharge) but why potential on plate B (negative) begin to rise above zero? Shouldn stay at zero? So intead of that we have 0V on plate positive A and +0.7V on plane negative B. So electrolitic capacitors can be charged in reverse connection? SECOND I dont understand at the beginning how C1 is charged. Both plates (A and B, positive and negative) are connected to the positive plate of supply. Q1 is blocked so plate A receive +Vcc (5 v) potential. But why and how potential on negative plate B begin to rise? And if begin to rise, plate A shouldn get some electrons from the plate B and loose some potential? Because Plate B is negative. Thankyou.
WOW! THANKYOU SO MUCH
If there was a resistor in the collector, is the emitter voltage still half of Vcc? If there was -Vcc in under the circuit ? Please answer
with a collector resistor you can have half Vcc on emitter by splitting the other half Vcc between the transistor and the collector resistor so the sum makes the supply voltage
hello sir , thank you for this valuable lecture, i have a doubt about the Rin which equal to 5k in your calculation , But Rin = R1//R2 + RinbaseAC R1//R2 = 9.2K and RinbaseAC= Beta (rtr +R3 ) = 100 ( 26+76) =10K => Rin = 10K + 9.2K = 19.5K not 5K ? Correct me if i'm wrong please
Bravo
Only time 🥳
Сan you please explain the purpose of R2 resistor? Look like capacitor will discharge through R2 if Vout < Ucap - 0.6v presents at op amp output. Is it expecyed behaviour? Will be better to connect this resistor to follower op amp output not to capacitor.
Can somebody explain me how the trans resistance (Rtr) is calculated (26mV thing)? Did I missed an earlier video ?
Hi, this is a canned formula that you have to accept. It is not something that you can derive. Hope this helps.
@@electronicsainteasy5253 Thank you very much.
not ve, ve is 10% of vcc, vce is half
Hi, what's the reason for assuming Ve = 1V for temperature stability?
Good question. I don t know I have never seen it explained.
It doesn t have to be 1 volt, really. What s important is that the 3 resistors, that is, the two in the voltage divider and the one in the emitter leg make the setup stable wr to beta, that is, changes to beta don t affect the bias voltages. I think i will makd a video of why it is so.
Since emitter follower doesn’t boost voltage, wouldn’t you want your input signal to be closer to the rail voltage of this stage if you were to drive a speaker?
As long as your output signal doesn't clip, sure. Buffers like that are considered considered current source to drive low impedance loads like a speaker. If you are doing audio, i think it's better to use op-amps which have very high input impedance and low output impedance. They are just easier to deal with.
Sharkit kapoj ni velu nathi tejanavo
Thanks for your comment. No idea what it meams though
nicely presented. thank you.
Thank you for your comment!
Alright. Not bad. I did follow but with 5V on the Vcc, and got Vc around 2.5V …. Now idea is to apply 0-3.3V via capacitor to base so it be -1.65 to 1.65V audio wave from DAC., boost it to 5V (can do 9V if necessary), then drive 1W 8ohm speaker. I’m assuming this stage boosts voltage, then will need current boosting stage.
yes, this type of circuit boost the voltage. think of it as a pre-amplifier. To drive a speaker, you need to boost the current, not really the voltage. Commonly referred as power amplifiers. If you do audio, you may want to look at op amps for boosting the voltage to proper level before your power amplifier.
So if my load is 4ohm speaker, then Rout needs to be less than 0.4ohm? Let’s say it’s a 10W speaker. So voltage to drive it would be v=sqrt(PR)=~6V. Therefore amplifying transistor needs to handle i=6/0.4=15Amps….. is my thought process correct?
For 10 watts you need about 5 amps to drive a 4 ohm speaker. So you would need a power transistor. Google 10 watt power amp transistor and you should find proper transistor to use then look at the datasheet for that Q and you might also get some sample schematics on the ds. Instead of Q, you can use ic like the LM 1875.
@@electronicsainteasy5253thanks. Just looked it up. Playing with bjts was more for education purposes also got quite a few on hands including them beefy ones. I like the 1875 too, will pick it up next time I’m ordering parts. What about using mosfets(or any fets for that matter)? They have high input impedance too right? Are they used for audio?
Note that what the video describes is for maximum voltage transfer, not necessarily maximum power transfer as the 2 are mutually exclusive. In the case of a speaker as load, you actually want max power transfer, not max voltage transfer. To accomplish max power transfer, you need a buffer amplifier (a voltage follower, basically) with high input impedance and low output impedance. That way, having a relatively high impedance at the output of your circuit (feeding into the speaker) is not an issue anymore. You could use a transformer too to act as a buffer. I talk about that in one of the videos about tube amps.
Should cover practical implications of picking the resistors. Eg. 100k/10k = 10x gain…but so is 1K/100. What would be the difference between each pair?
I made another video where I go into the details of picking the right value for voltage divider setup that sets up the bias voltage. Title of video is something like "common emitter design (part 1)". the key is make the design not dependent too much on the beta of the transistor. This gives you an equation in R1 and R2, and since you know the ratio, it gives you exact values for R1 and R2. No guess work. Note that the choice of R1 and R2 will also dictate (I believe) the input impedance of the your amp. Something to consider as you want that input impedance to be high, rather than load. Otherwise, you are gonna load down your source. Another reason to use op-amps for audio stuff.
Ok but now, what can I hook up to Vout? How much current and voltage will be at Vout?
I made other videos where I go into much more details. Especially the one about common-emitter amp design (part 1 and 2). Theory is nice and all but I highly recommend using LTspice or similar software to try things out.
@@electronicsainteasy5253 yes I just got into LT spice. What a time saver. Theory got me close but then to fine tune it I just kept adjusting resistor values till I get the behaviour I want. Thanks for the tip on using op amps. I don’t have much expertise with those that’s why normally opted for bjts.
I can't see the jump to the value of R2 at 30.48 time mark. What did you compute in your head to get that? Everything else flowed well.
Sorry i went a bit fast there. You have two equations for two unknowns. Using first eqn, you can express one of the two unknowns as a fumction of the other and you plug that expression into the second equation. It was not done in my head but on paper. Hope that helps
Can you please explain a bit more as I am struggling to see this. Also if I take R1 // R2 = 10k using your values I get 9200 is this correct. @@electronicsainteasy5253
This is a great video for explaining Thank you.
Thanks a lot for watching the vid and your kind comment!
Excellent explanation! Very helpful.
Thank you for your comment. Well appreciated.
signal generator as OUTPUT?????
input of course. Maybe it's the earphone used as a mike that's confusing. Earphone = high impedance mike (piezo-electric kind).
I like it , thank you sir !
Glad you like it!
Thank you very much for the amazing video! Because of your video, my brain got enlightened! However, here is my two cents (I think I am right. May be!!!): the collector's current is not perfectly rectangular; instead, just below base's voltage under 0.7 volt should be little curvy because, at little below 0.7 volt, the collector current is still flowing but much less than when base's was 0.7 volt.
Good point!
Thank you very much, that answers a lot of questions I had! THANKS
Great to hear!
nice circuit diagram there
Glad you like it!
Electronics ain't easy but your presentation is super easy~. I am impressed that, without using a preamp, you can still get a good signal.
Thanks for watching!
Hi bro nice topic❤❤❤❤😮
Thank you so much 🙂
Love it... great talent explaining the subject at hand
Thank you so much for the comment.
i remember buy it seems like yesterday
The old days when you could still walk into a Radioshack and buy one of those. Now, only available in secondary market as far as I know. But you can get those things very cheaply on ebay and the likes. Elenco still makes those nice ones but they are the snap-on kind, which I don't think are as good as the ones with the spring thingies.
i just love your channel, please lean towards rf electronics, my biggest dream is to be able to design radios and calculate values for components. A superheterodyne from top to bottom explained, from the input band, transistors impedance and impedance calculated for if filters would be a great series ... please try if you can...
Thanks for watching. I guess I could go into that. The good thing about superheterodyne radios is that any book on electronics will have a good description of what's involved. Of course, it won't have all the details on how to design the whole thing but all the steps will be explained. Then, it's a matter of studying each stage and designing each stage. I was gonna go into a different direction, like designing a synthesizer, but designing a radio is cool too. Food for thought, as they say.
Great work
Thanks a lot for the comment!
Beautiful
Thanks!
This is collage level math. Thev theory is too. I think you lost most people. But as an amplifier you must run the transistor in the active region to cut distortion I believe.
He said the resistor Rc in part I video was chosen at a value because of the halfway of the load line emitter current to incorporate the AC signal with the DC signal to be optimal (he taught that in the last lecture). That was a great part in his last lecture I enjoyed since it is more necessary in MOSFETs designs where high frequencies are in the amplified voltages using them over BJTs.
Yes, it s not easy stuff. I highly recommend watching part one first since i explain the dc bias setup. And you are absolutely right, the operaring poing or quiescent point should be at the middle of the dc load line so that the ac swings around the dc op point stay in the linear region.
Thank you for your comment.
A little clarification about RL, the load resistor. 2.2kohm is way too low if the supply voltage is 9V. If you look at the datasheet for the electret 6050, Vs = 2V, RL=2.2kohm and I=0.5mA. This gives us the voltage at the FET, Vf, using this formula: Vs-Vf=RL*I. So, Vf=0.9V. Now, RL can easily be determined for whatever Vs you have (should be between 0.9V and 10V though): RL=(Vs-Vf)/I. If Vs=9V, RL=16.2kohm. The greater RL is, the more gain the mike will have. To simplify things, I would use a 10kohm for RL (when Vs=9v).
Thanks for the info, exactly what I needed. If I'm powering the circuit from the camera battery (2s liion, 6 to 8.4v) then it would be best to use a LM7833 to get constant gain, right?
7:02. Lets not assume Q1 turns on at some point. It doesn't say much. :-) Q1 can only turn on if it gets current from the cap at Q2 which means a cap that is discharging. Right? But the cap at Q2 could not have charged since the collector at Q2 was at 0 volts due to current flowing through it. The cap can only charge if the transistor is off with its collector at 6V.
In the electronics for inventors book, the author makes the same assumption, which i think is very reasonable.
Can you please tell me the voltage Vce ? Is it Vce= Vcc- IcRe ?becoz there is no collecter resistance 🥺
Yes, correct for dc analysis. When looking at ac analysis, you need to consider Re ll Rload instead of just Re.