This channel is geared to those new to electronics. I try to keep the math relatively simple, i.e. no calculus ;). The plan is to cover all of the material a person would see in a two year college program.
The only reason to use a jfet is on the input to get a high impedance, after that i'd use bipolar transistors. That way you can get more voltage gain. You could possibly get all you want with 2 stages. An interesting idea would be a cascode where the lower device is a jfet and the upper one is a bipolar transistor
22:54 It looks good on small signals but if you increase input signal swing to few volts, output will be distorted (lower parts of sinus) because of the output capacitor. That is happening because emitter follower can't drain current, only source.
Not a very good cascode amp. There is no need to capacitive couple between stages, and some emitter degeneration in the cascode stage enhances stability. You can get much better frequency response for the same gain by buffering the input and output with common collector stages. This "Miller Theorem" is really a simplification and nothing multiplies or divides the capacitance. What is really happening is the shunt resistance across those capacitance is much higher in a common emitter stage and lower with a well designed cascode stage. An estimate of the frequency response of a multistage transistor amplifier is the inverse sum of the open circuit time constants. So when the shunt resistance is reduced, the frequency response goes up. Common collector buffers reduce the shunt resistance, and the resistance looking into the emitter of the upper transistor is much lower than if there was just a load resistor there ( in the case of a common emitter amplifier). I have built cascode amplifiers, written out all the node equations and used a program to calculate the high frequency rool-offs. I also used the estimate I described above and calculated about the same value. Finally, by measuring the high frequency roll-off, I found all were in close agreement. Your Miller Theorem" concept is erroneous, and you should understand that all transistor stages have gain. The common collector and common base configurations have current gain. In any amplifier you want power gain, so both current and voltage gain are needed.
Thank you for the excellent video! I am a self-taught EE hobbyist and only have hobbyist needs. I was considering building an In Amp from scratch for learning purposes, but due to the precision parts/resistors needed, I am considering an all-in-one package. With the gain of the AD2221 (correct #?) not reaching its expected goal and its function left uncertain, I am wondering two things... 1) Should I feel confident enough to use the 2221? 2) what other chips should I consider, having a price point of $20USD, or less?
Great presentation. Thank you. Question: I want to build a Sallen-Key filter for wspr on 20 meters. Do I have to worry about the slew rate on a 14 Mhz type of signal ? If so, can you recommend an op-amp that would handle this frequency level ?
Hola: Fantástica tu explicación acerca del ELENCO, aunque a veces es difícil de entender el inglés. También van mis felicitaciones por el extraordinario Laboratorio que posees. Desde Medellín, Colombia, te saluda, Ignacio Escobar Mejía.
As an EE and former extra-rated ham, I thank you for presenting the best presentation yet on a AM LC resonant loop antenna. I appreciate the RC equations as a functions of frequency. So long as you use insulated magnet wire to make the coil, it' shouldn't matter if the coils are right next to each other, so long as the wires don't get hot enough to melt the insulation and short out. I heard other AM broadcast band antenna builders proclaim a 1 foot by 1 foot square for making the loop. Are you sure 2 foot by 2 foot is the right value? I suppose will have to do further research on coil building to determine the inductance of hand-wrapped square loops.. I am hoping to find a source for the variable air capacitor for tuning this magnetic loop antenna. If you know where I can buy one, please post here. I hope to find one, so I don't have to run wire outside my house ( I live in an area where air temperatures drop below freezing for 2 to 3 months of the year), so I don't have to drill a hole in my house to string a grounded antenna outdoors with 50 to 100 feet of wire.
Professor please help!! When I was looking for MJE13005 datasheet I found there are two parameters named as VceO(sus)=400VDc and other is Vce=700VDC, so what does these two means?? Now which one is to consider as max withstand voltage rating when choosing this bjt to switch inductive load like smps ?? Please help
I just found this excellent video, thanks! I have one question regarding the last filter version, the "unity gain" without feedback resistors (using capacitors to set the desired damping factor instead). I guess this solution also can be used to get higher damping factor (skirt), but how do you calculate values for a second stage? /Regards Peter, Sweden.
I'm a little confused. You say at around 2.22 the pulse comes out of the collector. It appears to me the flow of the current is from 9v through R34 (which there will be a voltage drop) then to the collector through emitter though R33 to ground. You state the pulse comes out of the collector but it looks to me the pulse is produced by the voltage drop across R34. Saying the pulse comes out of the collector makes the current go the wrong way to me and doesn't make sense but I am surely no engineer. I see that there will be a pulse at the collector. Its just confuses me saying the pulse comes out of the collector. It looks like the pulse will be going "into" the collector resulting in a voltage drop across R34 and R33 with the pulse going through the primary of L5 resulting in an inductive kick which is amplified though more windings in the secondary of L5 then onward through the rest of the circuitry. Are you just saving time so you won't have to waste words tracing the current flow through all the resistors and oscillator transformer and coils?? I'm currently building this kit. Thank for your video and how to tweak things.
I wish you provided "homework", cause the only way to really learn is to use this over and over ... So I'm going to Moritz Klein's drum, snare and hi-hat videos to calculate what's happening. or I may just jump off a bridge if it doesn't work 🙂
Hi thanks for the video, I love it. Hope you could help me with the following question .... from the formula in the first slide n = Pout / Pdc, for instance, if type C power out was reduced dramatically but power from DC still reduced a bit but high, therefore n will decrease quite a lot too, means will not represent a high eff. Well, for this that's not correct and I'm misunderstand something.
At the negative cycle, the npn transistor should be in its off state, therefore disconnecting the 10V source from the pnp transistor, so where does the current comes from that allow negative voltage to appear at the output?
You can use this dinosaur also for high power boost and buck converters. The open driver collector and the open output collector and emitter allow the use of external low- or high-side drivers together with this device. You can connect the output emitter to ground and short the driver and output collectors and connect them across a resistor to a dc voltage of 12 V, which is also the operating voltage of the low- or high-side drivers. In this way it is possible to operate high-power MOSFETs for several 100 A of channel current. So, I have used the MC34063 as the controller for a boost converter which generates the power for a battery operated welding device of maximal 200 A at 30 V out of a Li-Ion battery with 22.6 V 100 Ah. The total input capacity of the power MOSFETs of 30 nF was operated with a MIC4420 low-side driver, which is capable to deliver a gate current of 6 A. The disadvantage of the MC34063 is its current limit detection differential voltage of 300 mV. So my shunt resistor is dissipating a maximum heat of 70 W, which is about half of the total loss of the power semiconductors (MOSFETs and Schottky diodes). But the efficiency is still well above 95%.
3 месяца назад
I would love to see more on the turret and bifurcated connectors. I occasionally work with them and would love to be better. I think if I was more skilled at turret connections they'd be my preferred connection style.
Sallen-Key filters should always be designed with the op-amp buffer gain = 1 in order to maximize the loop transfer function, thereby providing the best performance of the closed-loop op-amp buffer. Design is easy because the normalized resistors are one ohm and the normalized capacitor values are easily calculated based on normalized [w0 = 1 r/s] pole locations.
i have a question, maybe its a silly question. if the circuit is monitoring its own power. lets say the voltage reference is a equal divider (5v in, 2.5v ref). if the voltage decreases, the reference voltage will also decrease. eg, 3v in means 1.5v ref as far as i understand this video, the reference voltage calculation is based on a stable input voltage
The reference voltage depends on the In voltage as you said, but it isn't a division by 2, the reference voltage must be a lower voltage than the in one, like Vin= 3V Vref = 2V, for a lineal operation of the comparator . If you do a circuit with a Vin = 2V and Vref= 5V (for example), your comparator will work in no-lineal way, it will gives you in Output voltage the alimentation, Vcc+ or Vcc- depending were is the realimentation . I wish I answer your question, my english is not good at all :D.
Oh sorry I don't understad your qstion, yes, it will decrease in this case , bc he power the in voltage with 5V and then he divided the voltaje with 2 resistors with te same value and takes half voltage of the power(Vin).
HI, I love the clear explanations in these videos, the close ups of the test equipment certainly helps to understand how to test the circuits. I have however hit a problem with my kit at this AGC testing, at TP5 I only get 0.133vDC, the R38 is getting hot, I have tested R35, R36 and R38 (off the board) and are fine. Diode D4 is correctly orientated (also tried a replacement has there are 2 in the kit). So at this point I'm lost as what to do, I have contacted Elenco but as yet no reply. Any help would be greatly appreciated. Keep up the good work. (EDIT) C32 Faulty, I'll leave this post here if OK just encase anyone else comes across the same issue. ( I did test the capacitor before putting the board!)
thank you for the great videos. I prefer the capacitive reactance description of the detector output. the 2.2k resistor and 0.01uF cap form a voltage divider that is frequency dependent. where the voltage at the output is higher at the lower frequency signal.
I just wanted to thank you so much. I've always loved building electronic kits, Heathkit and I go back a long ways :) I picked up my first copy of this radio kit about 3 years ago and started building it. At the time I really didn't know much but this kit really piqued my interest and I found your videos. Wow, so much to learn... I didn't even have the basics down very well. So, I decided to learn more about radios and electronics. Over that time period I worked on the radio, took a break to study electronics in more detail, came back to build more of the kit and watched your videos again. Then I took a break, studied for my ham licenses and finally ended up with my Amateur Extra license. Now I'm back to my studies on electronics and have started anew on my kit. Each time I've watched your videos I know more from my studies which makes your videos make even more sense to me. I've got 3 of these radios, in different states of construction and I love making deep dives off how all this works while I build and study some more. In short, your videos are like candy to me. They scratch all my itches: electronics in general and the magical world of RF! Thank you for the time you've spent. You have done a service for many including myself and I'm deeply appreciative.
