Advice on Equivalent transistors

[Jpop]

how will u know when a transistor u have replace from the project schematics will work? or how will u know if it is an equivalent of the previous transistor?

[audioguru]

Experience. ;D

[prateeksikka]

some time spending and meddling up with data sheets and of course as audioguru said experience!
;D

[Guest Alun]

Yes, locate the datasheet for the transistor the circuit request and find and equivalent transistor with similar chariteristics.

[audioguru]

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

[Guest Alun]

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 F_T 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]

behavior of the transistor to unexpected surge voltages is also important to know when designing

[anis]

I am new user .I want information

[ante]

Hi anis,

Welcome to our forum.

Can you specify what kind of information you need?