totem pole output

Thread Starter

yassser

Joined Jul 25, 2011
91
hello,

does totem pole output stage(push pull) need a current limiting resistor to limit the current to the maximum allowed current , or does it limit the current anyway , I notice that when I connect it to a a small resistance load directly by mistake , it doesn't get burned , while it does in the case of open collector output .
 

chuckey

Joined Jun 4, 2007
75
A standard totem pole output (TTL) has a low value resistor in series with "top" transistor and Vcc and yes , its small, otherwise they could not get in the package :).
Frank
 

Audioguru

Joined Dec 20, 2007
11,251
A 555 oscillator/timer IC has a totem pole push-pull output.
It has nothing to limit the current to its maximum allowed 200mA.
But when the output switches high or low it causes a shoot-through current surge of 400mA.
 

BillO

Joined Nov 24, 2008
992
hello,

does totem pole output stage(push pull) need a current limiting resistor to limit the current to the maximum allowed current , or does it limit the current anyway , I notice that when I connect it to a a small resistance load directly by mistake , it doesn't get burned , while it does in the case of open collector output .
Some do and some don't. What device are you talking about?
 
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