Why are FETs preffered over BJTs nowadays? Does this have to do with higher switching speed. Also, if someone says that they are preferred due to low cost, please tell the industrial rate comparison of both.
8581
In my experimentation, I've used only BJTs as switches (for turning on and off things like LEDs and such) for my MCU outputs. I've been repeatedly told, however, that N-channel enhancement-mode MOSFETs are a better choice for switches (see  and , for examples), but I'm not sure I understand why. I do know that a MOSFET wastes no current on the gate, where a BJT's base does, but this is not an issue for me, as I'm not running on batteries. A MOSFET also requires no resistor in series with the gate, but generally DOES require a pull-down resistor so the gate doesn't float when the MCU is rebooted (right?). No reduction in parts count, then. There doesn't seem to be a great surplus of logic-level MOSFETs that can switch the current that cheap BJTs can (~600-800mA for a 2N2222, for example), and the ones that do exist (TN0702, for example) are hard to find and significantly more expensive. When is a MOSFET more appropriate than a BJT? Why am I continually being told that I should be using MOSFETs?
38356
I just started learning about electronics and decided to quickly sketch a circuit. When it comes to OP and changing the said circuit into an Ac equivalent, I got stuck. Sorry in advance if this is considered a basic question.
74477
Can someone care to explain - in plain English - what a transistor is and how it works. I know computers are full of these but don't know much about them.  P.S. I know about this site from another one in the family of StackExchange (I have no engineering background) and hoped someone might help me with this. Please don't link to the  explanation. I've read that and I'm more confused.   I'm looking for a 7 year old explanation.  Thank you!
38517
Could anyone help to analyze the circuit? I think block A should be a OP comparator. How about the other blocks function? Thanks a lot! The V1 is a adjust voltage source from a DAC between 4V to -4V
114108
Why are JFET/FET called voltage controlled devices while BJTs are called current controlled devices. Both require a voltage to operate properly. In both an electric field is produced so what is the difference?  Now the question is that current is also generated due to voltage and still BJT is current controlled and FET voltage controlled.
25751
Another form of the question is: will joining two diodes with wires (pn-np) make a transistor-equivalent?  I read that they are not equivalent, but why?
62257
Flash memory storage and EEPROM both use floating gate transistors for storage of data. What differs between the two and why is Flash so much faster?
7544
I have already posted a similar problem in the link above. I am facing the same issue in this circuit. What will be the state of the 2 BJT's Cutoff, Saturated or Active ? Please suggest me a generalised approach to tackle such problems.
10830
Why cant we replace diode connected BJTs by simple diodes in a current mirror circuit?
40949
On MOSFETs with multiple source pins, is the so-called &quot;Kelvin-connected source pin&quot; connected any different internally? Or is it just like every other source pin?   EDIT: Just to be clear, I am not asking what the Kelvin connection is for. I'm asking whether it is physically implemented any differently than the other source pins or whether it is just an extra regular, old source pin.
11341
Why does old PMOS/NMOS logic needed multiple voltages like  +5, -5, and +12 volts? For example, old Intel 8080 processors, old DRAMs, e.t.c...  I'm interested in the causes on the physical/layout level.  What was the purpose of these additional voltages?  Yes, this question is about stuff which was used 35 years ago.
102116
In a moment of cheapness, I decided not to order a 5v to 3.3v level shifter from Sparkfun, but instead to put it together myself.  The  used a  MOSFET, but since I enjoy surface-mount soldering about as much as root canal treatment, I decided to use a  that is through-hole mounted and easily available from my preferred supplier.  The results of this were sub-optimal.  When pulling the 5v line to ground, all was fine - the 3.3v side went to 0.07v.  But when pulling the 3.3v to ground, the 5v line showed around 4.14v (it was otherwise a touch above 5.1v).  On a closer reading of the datasheets involved, as well as the original Philips application note on the subject, I began to come to the conclusion that the gate threshold voltage was the problem.  By altering the schematic and tying the MOSFET's gate to 5v instead of 3.3v, both sides seem to work fine.  Pulling either side low causes the other side to go low.  I'm not, however, at all confident that this is actually a sane thing to do.  My understanding of the original schematic isn't deep enough to form a sensible opinion.  Will this modified schematic work, or are the current good results I'm seeing mere fluke or a precursor to something releasing magic smoke?
118899
The amplification of this amplifier is 1. So we have a buffer. But the question i wanted to ask was.    What can we tell about the current amplification of the circuit below? Is this circuit useful? I also found out that when i apply 8Vp-p at the input, i have a distortion at the output. Why does it happen around that voltage? or a basic explanation on it!
1533
I faced lots of circuits that has transistors connected as diodes (gate connected to the drain). I know some of these circuits employ such transistor for safety reason but I couldn't figure out the reasons of others.  My question: Is there any reason behind connecting the transistors as diodes other than the one I mentioned? Some of my colleagues suggest that they may be used to realize high resistance but I think connecting the transistor in such configuration (\$V_{g} = V_{d}\$) will force the transistor to work in saturation region, not in linear region. Am I right?
79435
Bought some "music speaker" thingies, some with bluetooth and some without. They are cheap, for sure, about 3 or 4 euro's. With some capacitor tweaks, they seem to be very plausibel to use (why is the output on these cheap things always tiny and limited?).  On these devices they use a very tiny, nice and bright display, with 7 legs, charlieplexed I suppose (wiggle it to see any screen update), 35 segments. Cannot read the number on the used chip (it's from JL), very hard to recognize (even when using a microscope) and the display doesn't have any partnumber on it either, however, these seem to be identical except the face plate on these components.   The displays are very interesting, just 7 pins to do the display job, in just one package. I want to buy these things (cannot find it, doesn't know the name and cannot find a datasheet either).   Next thing I want to do is to interface with these devices by reading the display (with a MCU for example) so I am able to read the state of the device and what it is doing. This is a difficult task without any datasheet.   Does somebody know the name of this component, is there a datasheet available somewhere?  Photo gallery of the display:          Product picture:
104185
EDIT:  Please read the whole post before automatically down voting. I KNOW the diagram is crap.  That is what I am asking about.  It isn't my diagram.  Original post:  I Web searched a bit and searched this site, but I didn't really see a good answer.  I thought line level voltage was insufficient to switch a transistor and I thought an audio signal coming out of an amp or preamp was a sine wave anyway.  I thought those things made the seemingly simple idea of driving LEDs to pulse with sound or music a little more difficult.  Microphone input -> preamp -> rectify it to make a nice fat on/off dc signal -> drive something.  But I see this:    with a circuit that looks like:   I see other circuits (one at Instructables I think) that essentially do the same thing- connect the line level voltage directly to some transistors.  My question: I haven't a clue what is going on here.  Why does this work- or does it really?  What is happening?  Is it that the "audio source" is really headphone/speaker level and not the line level it may be billed at and thus enough to saturate the transistor?  Does this look like a recipe for disaster?    EDIT:  Trying to focus things per Red Gritty Brick.  I know the diagram is crap.  How would you do it right?
103796
I was running through the datasheet of  (Low-Cost Low-Power 2.4 GHz RF Transceiver) which has a dimension of 2.40mm X 2.40mm approx. It was really amazing to find such transceivers to be fabricated in such a small area.Infact a transceiver requires a lot of R,C and even L.Resistors, Capacitors and semiconductors are easy to be imagined on an IC but an Inductor!!!  I haven't work in any VLSI industry so it would be great if someone can tell how these inductor logic is implemented on IC. Although it is said that  are alternative solution, but thanks for pointing if my knowledge is correct.