audioguru2
- Apr 6, 2004
- 12,026
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Experience. ;D
prateeksikka
- Jun 19, 2004
- 736
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some time spending and meddling up with data sheets and of course as audioguru said experience!
;D
;D
A
Alun
- Jan 1, 1970
- 0
Yes, locate the datasheet for the transistor the circuit request and find and equivalent transistor with similar chariteristics.
audioguru2
- Apr 6, 2004
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Hi Guys,
Most circuits use ordinary "general purpose" transistors.
If a circuit spec's a BC547 transistor then you can use a 2N3904 which is almost exactly the same (except their pin-out is reversed). ;D
Most circuits use ordinary "general purpose" transistors.
If a circuit spec's a BC547 transistor then you can use a 2N3904 which is almost exactly the same (except their pin-out is reversed). ;D
A
Alun
- Jan 1, 1970
- 0
But also note their main differences:
The collector-emmiter and collector base breakdown voltages vary between BC546 BC547 and 2N3904.
The gain varies between BC546A, B and C.
BC546xx only has a transition frequency of 100MHz, where 2N3904 has an FT of 300MHz.
The gain might not matter for a low gain device such as a buffer amplifier so it'll be alright to use a 2N3904 instead of a BC546C, but not in an audio amplifier which needs a high gain transistor.
The frequency won't matter in a simple light/dark switch so you could use a BC546 instead of a 2N3904, but not in a FM transmitter which needs a higher frequency transistor.
The trick is to understand what characteristics a circuit relies on to work properly - often it will say in the documentation, but check the voltage rating first then the current and maximum power dissipation ratings in circuits that use more power.
The collector-emmiter and collector base breakdown voltages vary between BC546 BC547 and 2N3904.
The gain varies between BC546A, B and C.
BC546xx only has a transition frequency of 100MHz, where 2N3904 has an FT of 300MHz.
The gain might not matter for a low gain device such as a buffer amplifier so it'll be alright to use a 2N3904 instead of a BC546C, but not in an audio amplifier which needs a high gain transistor.
The frequency won't matter in a simple light/dark switch so you could use a BC546 instead of a 2N3904, but not in a FM transmitter which needs a higher frequency transistor.
The trick is to understand what characteristics a circuit relies on to work properly - often it will say in the documentation, but check the voltage rating first then the current and maximum power dissipation ratings in circuits that use more power.
prateeksikka
- Jun 19, 2004
- 736
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- Jun 19, 2004
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behavior of the transistor to unexpected surge voltages is also important to know when designing
