Are All Transistors The Same

[Yury Morris]

Ido know the question in the title is really stupid, but it is the best phrasing I could come up with. Let's say I am building a circuit and the schematic says to use a BD139 transistor. Would there be any issue in using any other NPN transistor? What would I do if I could not find this transistor? I can't buy any parts online, and I do not have access to a store where they would sell this stuff, so I am limited to what I can salvage from old broken electronics, most of which have older, outdated parts that have limited information online.

Similarily, all electrical components have electrical characteristics and parameters. Different components can tolerate more voltages and currents than others. Others are set up for a particular application even though they are all part of the same family of components (capacitors, resistors, inductors, transistors, diodes).

You compare the parameters for the transistor you can have access too, and compare it to the one in the you want to have. You keep searching until you can find one that can handle it. Now, someone might have used an a transistor that was overkill for the project, and so knowing a bit about the circuit would help. If the current through a transistor was only 10mA and they have a part that can tolerate 1A, well, that's a bit much, and you can find a part that is more suited to what the circuit it. But if you do not have knowledge with how to analyse circuits, then you should probably match the component (to be on the safe side).

Often you can select a suitable test candidate based on technology (BJT, FET [enhancement or depletion mode], unijunction transistor, IGBT, MOSFET) polarity (NPN, PNP, N-type, P-type), power handling (case size, wire gauge), gain and gut feel.

Other more exotic parameters (capacitance, frequency response, leakage, voltage drops and saturations, etc) are seldom worth measuring if you have a part number as almost all transistor have on-line data-sheets. It is worth noting that often the marking is only part of the part number or in the case of an SMD components a part short code that corresponds to a standard part number.

BD139 is a pretty large power transistor (12.5 W with good cooling or short term), NPN, and can handle as much as 80V and 1.5 A. Its current gain can be as miserable as 25 in the worst case and I think most of other transistors of similar kind would handle this. It is not a high frequency transistor.

The substituting transistor must match or exceed these parameters. Without understanding schematics, it may easily be that some other parameters are even very important, but if the device cannot fail in a dangerous way and alternative is just to trash it, I would simply put a best available replacement transistor instead of the dead BD139 and try.

I have about 20 transistors of the same type, (in this case all BC547). But when I measure them with my 'trusty' transistor-meter it indicates that with some of them the emitter and collector switch places. Is this normal? I would think that there is a 'standard' pinout for these types of generic transistortypes.

For a given device number, transistor pinouts are pretty much always the same, even from different manufacturers. The only way I can think of that the transistors themselves would have different pinouts is if they were fakes.

I'm trying to make a H bridge with four BC337 NPN transistors. When I connect all the transistors bases to separate four arduino pins it works. But when I connect two transistors on the same pin (1 - 3 , 2 - 4) it's not working. Im sure the circuit is correct. I think Arduino digital pins can't supply enought current to 2 transistors because it's working when connected separately. How can I solve this?

Many H-bridges are made with all N-channel MOSFETs too. N-type silicon has better conduction properties than P-type, so there's a distinct advantage to using N-channel on the high side even though the driving circuitry (called a bootstrap driver) is more complicated.

Thank you all. I will check the wiring again. But I'm wondering is there a possibility of Arduino can't supply enought current to both transistors from same digital pin? I think it's 40 mAh maximum for output pins. Or should I buy some PNP transistors and make a H-bridge with both NPN and PNP transistors? Is it better? And can Arduino control PNP transistors?

No.

Two 500R resistors in parallel is 250R. So ignoring all the voltage drops that would make the current less, that is a maximum current of 5/250 = 20mA, well within the capability of an Arduino pin.

I'm trying to make a H bridge with four BC337 NPN transistors. When I connect all the transistors bases to separate four arduino pins it works. But when I connect two transistors on the same pin (1 - 3 , 2 - 4) it's not working.

You have chosen rather high base resistors for the low-side drivers, 150 ohms might be more

sensible if you want to be able to use the 0.8A capability of the BC337 in saturation. Even lower would

be better but would overload the Arduino pin...

As it is your devices will overheat at as little as 0.3A I reckon - the top two because thay are

emitter followers (not saturating at all), the lower two because the high base resistor value

prevents a decent level of saturation at full load.

At saturation the Vce should fall to 0.5V or less, meaning low heat dissipation at high current.

The base current will be 5 to 10% of the collector current. The transistor gain figure hfe

does not apply to a transistor in saturation.

Note the freewheel diodes which were missing in your circuit come to think of it, its drawn

swapped over from the normal layout for an H-bridge, sorry about that. The current setting resistors

(R5, R6) are tuned for the supply voltage and expected stall current to keep the devices in saturation

It's a cheap 3-6V motor and I guess max current is about 600mAh. Thanks for the circuit. I will try that one too. And should I use both PNP and NPN transistors? I see most of the H-Bridges are half PNP and half NPN. What are the disadvantages of using all NPN transistors? If half PNP half NPN is better then how should I connect them? (Like "PNP transistors emmiter to V+ , NPN transistors emmitter to V-" or opposite)

That mindset will get you in trouble. For a motor, it is easy enough to get the amps. Just use a ammeter (dvom) in series and check at voltage under load/no load. While it is running under no load, it might be 600mA, but grab hold of the shaft and stop it, get the reading, and let it go. Don't dawdle while stalling the motor or you can damage it. That gives the running and stall current, which might be well over 1A.

The main difference between a PNP and NPN transistor is the direction of the current flow. In a PNP transistor, the current flows from the emitter to the collector, while in an NPN transistor, the current flows from the collector to the emitter.

No, PNP and NPN transistors do not share the same formulas. The equations used to calculate the characteristics and behavior of PNP and NPN transistors are different due to their opposite current flow direction.

Yes, the same circuit can be used for both PNP and NPN transistors. However, the direction of the current flow and the polarity of the power supply must be reversed for the PNP transistor compared to the NPN transistor.

The choice between using a PNP or NPN transistor depends on the type of circuit and the desired outcome. PNP transistors are commonly used in high-side switching and amplification, while NPN transistors are often used in low-side switching and amplification. It is important to understand the differences between the two types of transistors and their respective equations to make an informed decision.

I started down my Fuzz ToneQuest at the beginning of 2018 - where I already had a few fuzzes, but determined that over the course of the year I would acquire around 30 of the very best fuzzes available across the different fuzz families. My aim was to get the bulk of my research done in 2018 so I could move on to investigating other pedal genres - like say Glitch/Granular Synthesis/Micro Looping.

As it happens though - I got to twice as many fuzzes as intended in 2018, and have acquired even more in 2019 - bringing that part of the collection to over 150 pedals as of this moment - split fairly evenly across all the major genres - Tone Benders, Fuzz Faces and Big Muffs, alongside Octave Fuzzes, Rats, Oscillating Fuzzes, Modulated Fuzzes and various other unique oddities and specialist Fuzzes. In the process of acquiring said fuzzes and building up this part of the Tone Library - I have developed a healthy fascination for the number and variety of different Transistors used / utilised for different purposes - so this post is really just a reference resource for and from my experience of different Fuzz Transistors to date - it is not intended to be any sort of comprehensive record of every single useful transistor type - just a record of my own encounters and a sort of notebook of what is generally out there and what I like in particular - I will treat it as a Work-in-Progress and edit and add periodically. Some of this data may not be 100% accurate as there are several idiosyncrasies within the transistor category - including gooping, counterfeiting, re-purposing and various inconsistencies in manufacturing and labelling.

Several of the established manufacturers were rather haphazard in their branding and quality control - meaning that the same transistor type often appeared in different casings, with different product codes / references - or on occasion no references at all. Lots of these operations did a fair amount of OEM manufacture also - making products for different companies - which means tracing the pedigree and provenance of several transistor families quite a tortuous and frequently nigh impossible process. There are also lots of Eastern European and Russian re-makes of popular types - often indistinguishable from the originals, while other are plainly counterfeit or mis-identified with the aim to confuse and mis-lead builders and collectors.

3a8082e126