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Replacements

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m.levin

New Member
I have been having a few problems trying to source the PNP and NPN transistors ZTX302 and ZTX502.
I have been trying to source an equivalent.
These are what I have proposed as replacements, but not 100% and would be great full for help in ensuring I get the correct ones.

ZTX302
Various
Si NPN Lo-Pwr BJT
V(BR)CEO (V)=35
V(BR)CBO (V)=35
I(C) Abs.(A) Collector Current=500m
Absolute Max. Power Diss. (W)=300m
I(CBO) Max. (A)=200n
h(FE) Min. Static Current Gain=100
@I(C) (A) (Test Condition)=10m
@V(CE) (V) (Test Condition)=6.0
f(T) Min. (Hz) Transition Freq=150M
C(obo) (Max) (F)=6.0p
Package=TO-92
Military=N

Possible replacement
BC337-25 TO-92 50V NPN TRANS (DIOTEC) RC (click for datasheet)

ZTX502
Various
Si PNP Lo-Pwr BJT
V(BR)CEO (V)=35
V(BR)CBO (V)=35
I(C) Abs.(A) Collector Current=500m
Absolute Max. Power Diss. (W)=300m
I(CBO) Max. (A)=200n
h(FE) Min. Static Current Gain=100
@I(C) (A) (Test Condition)=10m
@V(CE) (V) (Test Condition)=6.0
f(T) Min. (Hz) Transition Freq=150M
C(obo) (Max) (F)=6.0p
Package=TO-92var
Military=N

Possible replacement
BC327-25 SOT54A TRANSISTOR (NXP) RC (click for datasheet)


Thanks
Martin Levin
 

mneary

New Member
It depends on how critical the circuit requirements are. As you noted, the transistors are very similar. What is the circuit? Can you post it?
 

mneary

New Member
Looks like they are used as simple general purpose switches. Those subs should be OK.

I dou't find any spec on the ZTX302 for VbeSAT. If different, it would change the over-current cutout managed by Q2 and Q4.
 

audioguru

Well-Known Member
Most Helpful Member
The ZTX302 is very old and does not have the very low Vce-sat spec's of newer Zetex transistors. It is the same as all the other old little transistors.
 

mneary

New Member
The ZTX302 is very old and does not have the very low Vce-sat spec's of newer Zetex transistors. It is the same as all the other old little transistors.
I'm more concerned about Vbe-sat, but if it's just another old switching transistor then it shouldn't matter.
 

audioguru

Well-Known Member
Most Helpful Member
Vbe-sat is the input. You should care more about Vce-sat which is its output voltage loss.
 

mneary

New Member
Vbe-sat is the input. You should care more about Vce-sat which is its output voltage loss.
NO. I care more aboout the input voltage whether I "should" or not..

If you look at the circuit, the Vce is not important. Just about any logic level would be acceptable.

Vbe, on the other hand, establishes the conduction threshold of Q2 and Q4 and thereby sets the current limit..
 
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