Matched transistors
There are circuits that require matched transistors. Whether BJTs or FETs.
Like current mirrors, logarithmic amplifiers, etc.. There are some examples:
https://www.youtube.com/watch?v=DUlugLSroN8
https://www.youtube.com/watch?v=QY48IQXJIRI
https://www.youtube.com/watch?v=RpKEq5WyoLg
So I need matched transistors (multiple transistors inside one package). But I'm not sure whether datasheet must include magic word "matched", or basically any package with multiple transistors can be used?
For example this transistor is mentioned in one of those circuits:
PMP5201Y
but I have other dual-transistors like this:
BC857BDW
it doesn't mention they are matched.
I was expecting that:
- basically every dual or quad transistors are on the same die
- they are the same in terms of construction and therefore matched
Are these my assumptions wrong? Or there are some differences between "general purpose" and "matched" dual-transistors?
1 answer
If the data sheet doesn't indicate that the two devices are matched then sorry, they probably are not and, you should use a matched device like the PMP5201Y that you linked. That data sheet mentions "match" 16 times and 3 times on page 1: -
There are zero occurrences of the word "match" in the BC856 data sheet and, you can conclude from this that they are not specifically matched.
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