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Complementary transistor pair question
Complementary transistor pair question
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Old 19th April 2016, 07:20 PM   #1
aldovan is offline aldovan  Brazil
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Talking Complementary transistor pair question

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In a amplifier with complementary pair transistores , is possible use different brands ?
Per exemple, a TIP31 Siemens and a TIP32 Philips with matched gain ?
Or is a problem ?
Basic question, sorry...

Thanks

Aldovan
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Old 19th April 2016, 07:22 PM   #2
Welcome is offline Welcome  France
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TIP31/32 aren't particularly high standard transistors, so I'm sure there's a lot of variation between different parts. Therefore it shouldn't really matter much what brand you use, the results will be equally "poor".
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Old 19th April 2016, 07:36 PM   #3
aldovan is offline aldovan  Brazil
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Originally Posted by Welcome View Post
TIP31/32 aren't particularly high standard transistors, so I'm sure there's a lot of variation between different parts. Therefore it shouldn't really matter much what brand you use, the results will be equally "poor".
In my case I will use a AD161 Siemens and a AD162 Tungsram in A Philips Stereo amplifier.
This amplifier have a nice sound because use germanium transistors. Have problems in this combination ?
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Old 19th April 2016, 10:11 PM   #4
nigelwright7557 is offline nigelwright7557  United Kingdom
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Feedback in the amp should make up for any differences in transistors (within reason).

I use highly un-linear mosfet's in my amps and feedback fixes it.
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Old 20th April 2016, 12:07 AM   #5
Ian Finch is offline Ian Finch  Australia
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Complementary transistor pair question
Silicon transistors have very different Vbe (0.7V compared to about 0.25V for Germanium) so the bias voltage, bias control circuit and emitter resistors all have to be redesigned and modified considerably to correct the increased crossover distortion and different thermal compensation needs of Silicon transistors.

The circuit can probably be modified and a suitable bias control circuit could be designed and added to the amplifier to suit but the real problem is that the sound will never be the same as the original product.

I suggest that if you can buy similar germanium types, the best solution is to restore the amplifier to original condition. Otherwise, replace the power amplifier section with a suitable Chip amplifier kit or simply move on to a newer product that uses available parts (even though that is now becoming impossible too ).
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Old 20th April 2016, 12:23 AM   #6
aldovan is offline aldovan  Brazil
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In my opinion the best output push-pull circuit use two NPN or Two PNP transistores. The use of a complementar pair is poor, because the NPN transistor do not have the exact characteristics of a PNP transistor, aand each semicicle can sound different.
A tube output push-pull stage is best because use two tubes of same type.
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Old 20th April 2016, 12:44 AM   #7
nigelwright7557 is offline nigelwright7557  United Kingdom
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Quote:
Originally Posted by aldovan View Post
In my opinion the best output push-pull circuit use two NPN or Two PNP transistores. The use of a complementar pair is poor, because the NPN transistor do not have the exact characteristics of a PNP transistor, aand each semicicle can sound different.
A tube output push-pull stage is best because use two tubes of same type.
But the feedback loop takes care of any differences.
The bias setting takes care of the switch on of the transistor pair.

I have often used complimentary pairs and never had any problems.
I quite often use irfp240/9240 and they are quite different devices.

If it was a problem then a lot of amps out there simply wouldn't work or sound good.
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Old 20th April 2016, 12:48 AM   #8
aldovan is offline aldovan  Brazil
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You are correct.
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Old 20th April 2016, 01:58 AM   #9
hazard500 is offline hazard500  Australia
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Quote:
Originally Posted by aldovan View Post
In my opinion the best output push-pull circuit use two NPN or Two PNP transistores. The use of a complementar pair is poor, because the NPN transistor do not have the exact characteristics of a PNP transistor, aand each semicicle can sound different.
A tube output push-pull stage is best because use two tubes of same type.
I agree with your approach 100%.

However, I don't agree with your last sentence. My power amps feature 2 X IRFP9140 in push pull (choke loaded). You don't need valve amplifiers to use same type devices in the output.

That's why everything I design is differential. Much simpler than complementary design. And has has better PSRR and CMRR.
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Old 20th April 2016, 02:04 AM   #10
Ian Finch is offline Ian Finch  Australia
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Complementary transistor pair question
The crossover or rather the transfer characteristics of the upper and lower transistors in a Quasi-complementary amplifier is very different - even feedback can't remove the distortion as easily as it can with complementary output stages. That is the reason for using them. See figs. 2,3 here: http://www.keith-snook.info/wireless...0Amplifier.pdf
Even so, matched devices in close thermal contact can achieve very low distortion, as you find with Chip amplifiers.

Last edited by Ian Finch; 20th April 2016 at 02:17 AM.
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