What makes an audio transistor an audio transistor?
I particularly ask about bipolar transistors I am very new to this as I'm sure you willl gather as you read on.
Well to get things started on https://www.diyaudio.com/forums/analog-line-level/202458-pick-audio-transistor.html
#3 mentions "For Bipolars look at Hfe, Hie, Hre and Hoe and more critically how they change with the Voltage across the device and the collector current. You also need to look at how Ft changes with current changes and parasitic capacitance changes with voltage change. And then you may weep and go and use something else for audio, like tubes, that is actually suited for the job."
and later critically somebody mentions noise. But I can't find these changes only static Hfe ect in the following datasheets or noise figures.
Now looking at (for example) https://www.st.com/content/ccc/reso...df/jcr:content/translations/en.CD00003287.pdf
this seems like a brilliant transistor very fast transistor (its a switching transistor so no suprise) compared with the audio transistor https://www.onsemi.com/pub/Collateral/FJL4315-D.pdf
which I'm sure or at least I hope somebody will point out via the listed specs why it aint.
I particularly ask about bipolar transistors I am very new to this as I'm sure you willl gather as you read on.
Well to get things started on https://www.diyaudio.com/forums/analog-line-level/202458-pick-audio-transistor.html
#3 mentions "For Bipolars look at Hfe, Hie, Hre and Hoe and more critically how they change with the Voltage across the device and the collector current. You also need to look at how Ft changes with current changes and parasitic capacitance changes with voltage change. And then you may weep and go and use something else for audio, like tubes, that is actually suited for the job."
and later critically somebody mentions noise. But I can't find these changes only static Hfe ect in the following datasheets or noise figures.
Now looking at (for example) https://www.st.com/content/ccc/reso...df/jcr:content/translations/en.CD00003287.pdf
this seems like a brilliant transistor very fast transistor (its a switching transistor so no suprise) compared with the audio transistor https://www.onsemi.com/pub/Collateral/FJL4315-D.pdf
which I'm sure or at least I hope somebody will point out via the listed specs why it aint.
Basically a DC amp with a bit better high frequency performance, like the 2N3055 designed for series pass in power supplies.
It depends what kind of audio transistor - input of a low noise amplifier is different from a VAS stage in a power amp is different from a power output device, but mainly a combination of properties that minimizes common distortion mechanisms and noise across the audio band.
Distortion mechanisms vary according to the use of the transistor, for instance the Early effect may be important in one circuit and not in another, and for output devices its good for gain not to drop at high currents.
For an MC phono stage low voltage noise is very important, distortion much less so due to the very low signal levels (distortion always falls with signal amplitude)
Lack of popcorn noise is another clear audio-friendly property!
Distortion mechanisms vary according to the use of the transistor, for instance the Early effect may be important in one circuit and not in another, and for output devices its good for gain not to drop at high currents.
For an MC phono stage low voltage noise is very important, distortion much less so due to the very low signal levels (distortion always falls with signal amplitude)
Lack of popcorn noise is another clear audio-friendly property!
The quick answer is that there is no such thing as an audio transistor, except in the sense mentioned by PRR in post 3.
A longer answer is that some transistors are designed to have, or happen to have, characteristics which may be useful in certain stages in an audio system. For example, low noise (or, at least, a low 1/f corner frequency) is useful in a low level input stage (whether for audio or other low frequency applications). Current gain linearity can be useful in an output stage.
A longer answer is that some transistors are designed to have, or happen to have, characteristics which may be useful in certain stages in an audio system. For example, low noise (or, at least, a low 1/f corner frequency) is useful in a low level input stage (whether for audio or other low frequency applications). Current gain linearity can be useful in an output stage.
In former times there were high power devices such as the 2N3442. They were designed for linear PSU's, had transition frequencies in the tens of kHz and weren't good for audio. But with the manufacturing technologies and knowledge we have nowadays? Hence - see PRR!
Best regards!
Best regards!
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