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I am wondering, why is there no complementary transistor pairs to buy, since their use as individual devices is pretty common in audio amplifier applications.

So for complementary transistor pair it is desired to have as identical properties as possible (gain, bandwidth, breakdown voltages, etc.) - it is hard for an amateur like me to find two very closely identical transistors (one pnp and other npn; for BJT lets say).

  • Are there any (power) complementary transistors available in any electronics shop? If there are any, example of them would be great!
  • If there are no such transistors in one package sealed together, why is there no one manufacturing such components?

enter image description here

One more thing. I have recently bought a lot of cheap npn and pnp transistors of same model (npn->BC337 & pnp->BC327). I have found two almost identical transistor, as the thing concerns of the gain which is approx. 320 for both. Sadly transistors are low power and cannot be used in power amplifier in the driver stage, where currents get amplified to greater levels (1 amp and above).

I kind of modified these two transistor so I can use it (two pieces in one) on the breadboard - if one starts heating, the other also starts heating for the same portion; making them work in as identical conditions as possible.

  • What do you think of this "modified version" of two transistors as one transistor? Bad, dumb, nothing special, awesome?

Transistors are pulled together with thermal shrinkable tube :D enter image description here

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  • \$\begingroup\$ Trying to match transistors -- especially complementary types -- is not scalable to mass production, because the labor costs are too high. This is why you won't find any commercial offerings. It's far better to design your circuits so that they don't depend on the exact characteristics of the devices or how well they might be "matched". \$\endgroup\$ – Dave Tweed Sep 20 '17 at 15:13
  • \$\begingroup\$ The market is just tiny, especially since you won't be willing to pay the costs of 10s of bucks for simple transistors. npn and pnp are different enough that matching all the criteria you wanted is mostly luck in single transistor productions. \$\endgroup\$ – PlasmaHH Sep 20 '17 at 15:16
  • \$\begingroup\$ They exist and they throw in the opamp for free, called a power amplifier \$\endgroup\$ – sstobbe Sep 20 '17 at 15:53
  • \$\begingroup\$ Opamps are not precision transistor pairs. Most of the matched pairs today are used in precision-analog electronics, hence are low-power. The good ones also cost a premium. Eg the Intersil HFA3046/96/127/128 family cost 5 to 10USD per piece. \$\endgroup\$ – Attila Kinali Sep 20 '17 at 17:11
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    \$\begingroup\$ Your thermal-tracking bandwidth will be poor ---- low Hertz, because of the high specific-heat of silicon and the poor thermal conductivity (high thermal resistance) of the epoxy cases. \$\endgroup\$ – analogsystemsrf Sep 21 '17 at 4:20
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Paired complementary transistors may be in separate packages (old solution), or in combined (e.g. 6 pin) package. Matching of NPN and PNP transistors may privilege only a few parameters. They may be switching times, capacitance, gain, etc. Depending on your design some are more relevant than others.

There are several choices.

BC846BPDW1, ON Semi, SOT-363, VCEmax=65V, ICcont=100mA

CPH5524-D, ON Semi, SC-74, VCEmax=50V (100V for VCBO of NPN), but ICcont=3A

PBSS4112PANP, NXP Semiconductors, has maybe a difficult package (DFN2020-6), but VCEmax=120V, ICcont=1A

PBSS4160DS, NXP Semiconductors, SC-74, lower VCmax (60V), ICcont=1A. Both NXP can be used for low VCEsat applications.

SMBTA06UPN, Infineon, VCEmax=80V, ICcont=500mA

So , you see that low and medium collector currents can be accommodated for, and voltages up to 100V. To my memory the maximum VCE voltage for matched pairs is around 150-200V.

A power transistor with large VCEmax (200V), ICcont=10A, that is sold as separate TO-3P for NPN and PNP is FJA4313 and FJA4210.

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  • \$\begingroup\$ Nice. The last FJA transistors you mentioned, it seems that only PNP version exist, no NPN sadly. \$\endgroup\$ – Keno Sep 20 '17 at 18:01
  • \$\begingroup\$ Just checked on mouser.ch (equivalent to other mouser sites) and both available for about 2 Swiss francs each. There is also a smaller version, I don't have the part numbers ready with me, now. \$\endgroup\$ – andrea Sep 22 '17 at 22:19
  • \$\begingroup\$ The other two made by Fairchild are FJP5200 (1.6 $) and FJP1943 (about 2 $), lower power variants of the two FJA above. And now I have found the issue: I was always thinking the right part number for NPN (FJA4313), but typed it wrongly in the answer ("4213"): amended, sorry. \$\endgroup\$ – andrea Sep 23 '17 at 8:47
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ON Semi has a line of matched transistors for audio. Some of them include a diode in the package for class AB operation. This allows the diode to track the temperature of the BJT very accurately.

Here's a matched pair datasheet: ON Semi audio BJTs

Here's a datasheet for the "Thermal Track" transistors: ThermalTrak

So you can see your idea about co-packaging your transistors for thermal tracking isn't bad, though the thermal coupling through the mould compound probably isn't very good.

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