BJT and PMOS switch question

Thread Starter

jerome89

Joined Jan 14, 2013
5

R1 to R6 is 470 ohm
Vdd is 20v
the arrow is connected to gate of PMOS, PMOS is sharing the same Vdd 20v

may i ask, why is there no resistor on the base of NPN ? if theres one, what is it used for ?
what is the purpose of R1 to R6 resistor?

sorry, my electronics is really horrible, i hope you can clear my doubt
thanks
 

Alec_t

Joined Sep 17, 2013
11,880
The ULN2003 has Darlington transistor outputs, each with an in-built 2.7k base resistor.
R1-R6 are collector loads acting as pull-ups.
I can see no purpose for Q1-Q6 unless they merely represent the ULN2003 output transistors.
 

Thread Starter

jerome89

Joined Jan 14, 2013
5
The ULN2003 has Darlington transistor outputs, each with an in-built 2.7k base resistor.
R1-R6 are collector loads acting as pull-ups.
I can see no purpose for Q1-Q6 unless they merely represent the ULN2003 output transistors.
yes uln ports connected to pic microprocessor
why R1-R6 is 470 ohm and not higher or lower?
 
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