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97 Threads found on edaboard.com: Transistor Hfe
hfe is used with a linear transistor that is not saturated, the datasheet shows a Vce of a few volts to 10V. The datasheet for most transistors shows the saturation voltage drop when the base current is 1/10th the collector current disregarding the hfe.
A common emitter transistor is an amplifier. It amplifies its collector to base (icbo) leakage current.
Hi, I'm trying to understand the fundamentals of transistors but I'm having a hard time with getting my circuit to work the way I want in real life. My circuit is a basic common emitter configuration (I think): 132791 The beta value of the transistor is 150, so I calculated the current through the collector resistor
By design method, any architecture can realize a constant current gain(beta) over a large input (ib) range? Unlike the typical current gain as shown in this figure, the gain should be a constant line. 131995Don't know of any way to do that. Normally the voltage gain of a transistor is stab
Hi, I need to measure hfe of a NPN power transistor with 5A of collector current. I found a lot of of circuits to measure hfe but no one has this characteristic. Regards, Fernando - PU2PLL
I'm trouble-shooting a pre-amp from a 70's Fender Rhodes electric piano. Pretty simple device... but I realized that I should poke around to see what equivalent transistors I might need. With rare exception, the designer selected 2N3392s for his go-to transistor. Amplification, buffering, tone controls... all 2N3392s. The top rail is 25 V, sing
I am learning S53MV oscillator design. It is provided here: I want to understand how biasing was chosen for BFP420 bjt transistor. I cant find any I-V (Ib) curves in BFP420 datasheet. Prevously i biased FET ne3210s01 and it was pretty convient, because there was some I-V curves, where i can draw
I do not like the way the input transistor is dc biased. It is likely that transistor is fully saturated (collector voltage either at 0v DC or at 3V dc, instead of what it should be around 1.5 v DC). you can measure collector voltage with a voltmeter
KSC388 (npn transistor) datasheet page 2 says it has a hfe of 20 to 200 However, graph on page 3 (fig2) shows its hfe is around 110 to 150. Which page is right? KSC388 NPN datasheet
With an Rb of 15K, you need to make sure that the transistor just goes into saturation. So (Vcc-.8)/15K = Ib. therefore Ic = hfe X Ib, so Rc =(Vcc-.3)X 15K/ hfe X (Vcc-.8) or ~ 15K/hfe. 1K would do. Frank But most transistors do not saturate if their base to collector current is defined by (...)
It's pointless to compare audio low noise with RF transistors. Unfortunately you didn't even mention the frequency range of interest, particularly does the noise corner frequency matter?
No problemo, sorry I took it the wrong way. I think I just need to look for a cheap switching TO-3 NPN transistor , maybe 250V or higher with about 10A capability. I'm going to try a BUX32B. Try if you like but it has poor gain and Rce hfe= 8 ~40 @ 3.0/6.0 (Vce / Ic ) implies Rce= 500 millOhm 8 is low
Your Japanese transistor datasheet is missing important information. American and European datasheets list the maximum saturation voltage in writing and show the "typical" saturation voltage on a graph. Note that the base current is 1/10th the collector current regardless of the hfe. There is a big difference from typical to maximum.
One other thing, notice they haven't quoted a quiescent current? When I have one connected to a circuit it drains the battery when left idle, that's why I decided to toggle the power using the transistors. Before making things complicated, try measuring the current again with the DATA pin tied to ground, my experience of these kinds
You can take a search at the website bellow, by changing some parameters in order to relieve the specifications so that better fits to your need:
Simply look at the datasheet of the switching transistor. Here is a little 2N3904 transistor switching a 50mA current and a big 2N3055 power transistor switching a 10A current:
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 (...)
You don't need to calculate the base current depending on Vout. You need the base current for I out. Say you want 16V out and the Vbe of the transistor is 1.2V then you need to set the base to 17.2V to get 16V out. If your load at the emitter draws 1A at 16V , then your base current (assume hfe of 1000) will be about 1mA. Whatever the base is
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
Ib = Ic/hfe so for 1 Amp collector current, the base current will be 1/hfe. In theory, any transistor with a collector current rating of at least 1 Amp and a hfe of at least 40 could be driven by the PIC. There are thousands of such devices on the market but not all may be avaialble locally to you. Please note that those (...)
I think your estimate for current through R6 is pretty accurate. However, diode drop (ssumed 0.7V) is also slightly current dependent, so you should check on data sheet and re-iterate if you want to be very sure. Regarding base current: It is quite small, but because it is dependent on hfe (the current gain) of the transistor It will vary aa lot
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).
Ib > (Ic/hfe) Use a value of Ib that is much greater than Ic/hfe, to ensure that the transistor is fully on (saturation mode). Hope this helps. Tahmid.
The measurements with a multimeter hfe tester are meaningless. SD1275 current gain is > 1000 (as with any darlington). But the transistor has integrated resistors that give a low hfe reading with the low currents used by the hfe testers.
They used this value to make sure the transistor is fully saturated at all values of hfe/volt drops across D1/10 ohms o/p of NE555. . . Frank
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
One problem is that the collector load for Q2 is a transformer. This will have a very low DC resistance ( .5 ohms?) so the output stage will have a potentially huge current before it saturates. Lets presume an output current of 5A, the darlington transistor will have a hfe of 1000 or so, so the base current ot get this is 5/1000 = 5mA, as there ar
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 (...)