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81 Threads found on edaboard.com: Transistor Hfe
A transistor in a TO-220 case is usually used at 1A to 3A, not at just 0.0025A like your tester uses. hfe is not used when the transistor is a saturated switch anyway, usually the base current is 1/10th the collector current for a switching transistor but at higher currents the base current might need to be 1/3rd the (...)
Aren't the output transistors a complementary NPN and PNP pair of emitter-followers? Then if the NPN is cutoff with a Vce of 69V the PNP is saturated with a Vce of close to 0V or close to the negative supply voltage, not 38V. hfe does not matter if the driver transistor can supply the maximum base current needed for the output (...)
You NEVER EVER make a common-emitter amplifier like that. The base current for one transistor part number has a wide range (the hfe value) so some transistors will be saturated (high hfe) and other transistors will be cutoff (low hfe). Negative feedback is needed to effectively reduce the (...)
Hi, In linear power supplies there is a transistor (usually darlington) that is current-controlled depending on the output voltage. The problem is I cant seem to find the Vout - current-to-darlington-base equation. Do I operate it in the linear region? When Vout < Vout_desired do I saturate it? What is the range of current in its base? (i
Darlington's have the disadvantage of almost 2 diode drops initially ( actually 1 diode drop & 1 saturation drop) but when conducting heavy currents with fast pulses in PWM due to low input capacitance compared to MOSFETS will have better current gain( ~100) . When the transistor is used as a switch and saturates, the hfe typically reduces to o
How can I simulate a circuit using 2SC1969 transistor in ADS? i don't think there exists a model of 2SC1969. So how can I simulate?
Your emitter capacitor C1 shorts the emitter resistor which kills all AC negative feedback. Why is the DC collector voltage so high that the transistor is almost cutoff? I simulated it and got a voltage gain of only 30.1 times. I corrected the bias so that the DC collector voltage is 6.3V and got a voltage gain of 181.3 times. Without any negativ
There is a different class of transistor switch with ultralow Vce and Rce with higher hfe and gain at saturation. I wont get into the epitaxial differences but instead of 10:1 Ic:Ib specs for switch operation they are 50:1 and usually specialized by Diodes Inc and some others. They also class the devices for NPN with Rce like MOSFETs
I'm searching for another pair of transistors but all i find with suitable voltage/current ratings have approximately the same hfe. There is something I don't understand and are missing, but what? When designing power supplies with discrete transistors, you should also consider other circuits than single (...)
The capacitance of a transistor and its wiring is a filter and produces negative feedback from the collector to its base due to the Miller effect which reduces the hfe AC small signal current gain. The hfe DC small signal current gain is not affected so it is the highest. Fairchild's datasheet for the 2N3904 transistor (...)
Friends I am new in RF design. I want to design a class A power amplifier at 850 MHz by ADS. How to calculate Zin and Zout of transistor Q2SC5761_M16 for input and output matching network. hfe of transistor Q2SC5761_M16 and QN3440 are 300 & 100 respectively. Graph of Vce Vs ic is correct but graphs of Zin and Zout are wrong. 10
If I remember my transistor circuits, the output impedance of a common-collector transistor is the emitter resistor (100K, in your case) in parallel with (input impedance)/hfe. Thus, you're still going to have a pretty high output impedance (maybe around 50K). Can you use a lower value emitter resistor?
Question is pure theoretical. Input impedance equation should be solved using four-pole parameters of transistor. Expression is needed and not numerical result.
BC 546/7/8 is one of the most used general purpose transistors, so don't worry about availability. If you want that any BC548 type can be used (A, B or C), calculate the resistor for the A version. If you can have some power consumption from 3.3V, just go for 1 mA, this will sure saturate the transistor. At low temperatures hfe drops and (...)
It's unclear what causes the distortion. With MPSAxx transistor models you see only small deviation from ideal waveform. Although current mirors might be not well matched, this won't cause nonlinearity.
Well, I'm not sure I'd say it this most important thing to know... There are a number of things you need to consider in selecting the transistor, in no particular order: What voltage will it operate at? What is your current load? What is the available drive current and voltage? How fast do you need to switch your load? As far as hfe, a rule of th
Would it be smarter to use a transistor with min hfe of 100 or min hfe of 250? hfe is AC current gain and has almost nothing to do with AC voltage gain. Since your buffer is an emitter-follower it does not have any voltage gain anyway. When the AC hfe is high then the DC hfe is also high (...)
Bruno, At the page bellow, you can find 2DC5609 parameters : Clicking at 2DC5609 equivalent, results in that parameters : In fact, the only
I have a heavy load to drive with a PIC and I want to use an NPN transitor with load on Collector. I'm looking for a transistor that starts conducting with a very low current on base, low enough to be driven with a PIC (TTL out, 25mA max). I also need high current on Collector (around 1A). To better explain the way I'm going to use it, here's the
Hello I have this simple current source circuit and the current source through the collector is controlled by voltage drop across the transistor base emitter and resistor R5 Ic=Ie = Vbe/R5 but i want to know how much current flowing through the base and diodes ? The current flow through the resistor R6 = (9-1.4)/1K = 7.6mA i supposed the to
The circuit in post 1 is quite easy. You can simplify it like in the pic below. The circuit in post 3 is much more difficult. There are 2 possibilities: If the transistor is saturated, then we can estimate Vce = 0.1V. If the transistor is not saturated, then Ic = Ib * hfe. In either case you need to write out a set of l
Software for ease of calculation. transistor.rar --- with installation transistorS.rar --- no installation
The circuit doesn't provide reliable current limiting. The maximum output current depends on input voltage and transistor current gain.
Hi all, I have to perform an experiment on my own. Experiment title is 'find H parameters of BJT transistor'. I don't have a clue what to do. I am asked to show hie, hfe, hoe calculated values in lab that should match to specification sheet of transistor. please tell me how to proceed step by step. Thanks in advance.
I'm guessing you are ignoring base current and hfe in your assumptions. I am afraid, boylesg is not familiar with transistor basics (operation principles).
How to calculate base current of a NPN transistor with collector current 50amps?..
because there is no such transistor with those specs 2SD1275 is rated 60V and 2SD1275A is rated 80V
Columns are A -> G Rows are 21 -> 24 IB= column contains the formula =E21/C21 RB= column contains the formula =(B21-D21)/F21 They are based on the equations here:
What transistor are you having Most Multimeters have hfe detectors use them they are more helpful if you want to know whether your tranny is working or not
Never mind the 555 and everything to the left of it - have a good understanding of that part. But I don't understand hoiw the designers of the circuit (below) have come of with the resistor values on the base of the BC327 and the base of the Darlington. I have had a stab based on a 555 puting out from 50 to 100mA but I have not come remotely near
Hi My friend I don't know that is there any site available or no , but i want tell you if i have the problem like your problem what i will do : I will read it's datasheet and write maximum IC and hfe and GBTP of current and break voltage , in a paper and try to compare them with transistors that i have ever used or know , or will search in my da
can i use BF494 transistor in place of BF199 transistor and BC549 transistor in place of BC547 transistor ?
what i can tell you is hfe is the beta gain of the BJT. It is given in datasheet of the transistor. I don't exactly know about the other two parameter. Umair ---------- Post added at 23:31 ---------- Previous post was at 23:21 ---------- what i can tell you is hfe is the beta gain[/B
You need to stop thinking about the transistor as a resistor... it acts like a diode, so best to think of it as one. Here are your steps to analyze the circuit: Need Ic = 10 mA (max) Most BJT's need 0.7V across the base-emitter junction to turn on. Looking at hfe (DC current gain) on the spec sheet, you'll see that a BC109 has a minimum (...)
I wanna know exactly how a transistor amplifies any signal
Hello All, I am trying to work with M34063 with 2SB1386 transistor for stability. There is a lot circuit diagram about these combination on internet. What I want to ask is, Initially when i brought the transistor 2SB1386, its was 2SB1386Q i.e. hfe range 120 t0 270. Now i am not able to find the same, What i got is 2SB1386R. When i
Hi, I buiding simple transistor switch circuits using 2n2222. I looked at the datasheet for the value of hfe.the datasheet gives many values of hfe. how do I know which value to take for my calculation. the values range from 35 to 300. please help me with this. thank you.
how much difference will a transistor with hfe 15-20 & 20-25 will bring to the circuit while all other parameters being same.
Hi, I'm pretty new to the forum. So I hope I posted on the right channel. I want to ask about the measurement condition that is put next to transistor parameter. I have BC846A from NXP. The datasheet can be downloaded from here. The datasheet sa
I assume that the datasheet minimum is the minimum you can find in components but there are many different brands of the same transistor, maybe the minimums are not the same for all of them. When you have an emitter resistor you don't care about that (assuming that your source can provide the base current), the base current will be as much as need
Thanks for quick reply. Do you know any transistor with diode built in? I am looking for something with Ic ~3A and hfe ~500.
The datasheet for every transistor part number gives a range for hfe. It also shows the hfe changing with collector current and temperature. You should design a circuit with enough negative feedback so that it works when the hfe of the transistor is minimum or maximum and also works with the minimum and (...)
crazyjohn, Follow the simple BJT eqautions, transistors have same basic eqations relating all its parameers like Ic, Ib, Vce,Vbe,hfe etc. First check it with given values in data sheet. then you calculate required value with available values of other parameters. And well, if you designing something, the dig every thing until you satisfy....Give m
Ive got a npn transistor circuit set up in a emitter amplifier configuration.Ive set the base voltage at 5v though the voltage divider and set RE to drop the remaining 4.2v at 50ma which should control IC and IE current. The problem is how do i calculate the value of r1 or r2 of the voltage divider so that it will output 5v even after being conn
Small variations in the base current will have big variation in the collector current. Check transistor explanation in the following link Tutorials, Electronics made EASY, Williamson Labs Alex
It is mainly limited by transistor heatsink capacity, acording device SOA specification ( see datasheet )
Quick calculation : 100Watt at 10V input voltage (neglecting efficiency of the system) = ~10Amps in the transistors. The transistor you choose is not good. Maximum,specification only 6 amps. hfe in the order of 30 for high currents, this means you should need 333mA base current at 10Amps, not good for the 555. You need better (...)
How do you know which hfe value to use from a transistor data sheet in biasing a bipolar npn transistor in common emitter to get desired IC current when Ib current = IC/hfe is applied ? Take a bc548 npn transistor for example how would you calculate the biasing current required on the base to get a (...)
First Hi to All the People because it is first time I am writing to any Forum. I am doing B.Tech in Electronics I have read hundred of Books on transistor but didnt find much details regarding basic concept. For example transistor 2N3904 has a maximum Ic 200mA and generally in all the books its DC gain is given as 100 but when you read data sheet
Apart from the fact, that the Early voltage model is a simplification that won't be exactly met by a real transistor, I wonder how you measure hfe of the first transistor of 6N139, as the base terminal isn't accessible?