Complementary Transistor Pair

Question

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?

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

Answer 1

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.

Answer 2

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.