Datasheet Question

Thread Starter

waldopulanco

Joined Nov 14, 2013
26
i was wondering on how to read a datasheet for transistor i mean i mean if i want to bias or operate the transistor how to prevent it from damaging,
i have read the data sheet and i want to know some basic info example


Rich (BB code):
collector-base voltage = 55V condition open emitter
 

 Collector-emitter voltage = 55V condition RBE = 10 Ohms
 

 Collector-emitter voltage = 30V condition Open Base
 

 Emitter-base voltage = 3.5V condition open collector
 

 Collector current(DC) = 0.4A
 

 collector current peak value = 0.4A
 

 total power dissipation = 3.5W condition up to Tmb = 25 °C
 

 storage temperature = +200 °C
 

 junction temperature = 200 °C
 

 Power Output  = 1W

Please can you explain it!! i want to know some basic information in datasheet!!


Thanks in advanced!!
 

crutschow

Joined Mar 14, 2008
34,285
I would think you understand some of those data sheet values. For example it would seem apparent that you shouldn't ever exceed the voltage, power or current ratings when using the device in a circuit. Which ones do you find particularly confusing?
 

Thread Starter

waldopulanco

Joined Nov 14, 2013
26
I would think you understand some of those data sheet values. For example it would seem apparent that you shouldn't ever exceed the voltage, power or current ratings when using the device in a circuit. Which ones do you find particularly confusing?

As an example the total power dissipation is 7 watts, what wattage can only apply during operation to avoid destroying the transistor? half of the total power dissipation or 3.5watts or 2watts?

thanks!!
 

Alec_t

Joined Sep 17, 2013
14,280
As an example the total power dissipation is 7 watts, what wattage can only apply during operation to avoid destroying the transistor?
You should always design a circuit such that the transistor operates well within its ratings. The bigger the margin you allow, the longer the life of the transistor is likely to be. With few exceptions I would aim to keep voltage/current/power at no more than 70% or so of the maximum.
 

crutschow

Joined Mar 14, 2008
34,285
As an example the total power dissipation is 7 watts, what wattage can only apply during operation to avoid destroying the transistor? half of the total power dissipation or 3.5watts or 2watts?
For that amount of power you need a heat sink for the transistor as MrChips stated. You need to look at the thermal resistance of the transistor junction-to-case (θjc given in °C/W) and then determine the thermal resistance of the heat sink you need to dissipate the power at the highest ambient temperature the device will see while keeping the device junction temperature below its maximum rating by at least 25°C.
 
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