ULN2003 to run at bigger amp

[same79]

I have an idea in attached circuit to use ULN2003 to drive stepper let say, at 4 amp. Please guide me is it possible and what will be its frequency rate (step frequency limit per second)?

[john_100]

Hi Same79 ,

the ULN2003 has open collector outputs
to drive the FET's you need pull up resistors between the output and +12V supply

or an active pull up circuit for high speed operation
as you need to be able to charge and discharge the gate capacitance

another way depending on the motor voltage
is to use 4 ULN2003 IC's
check the data sheet , but I think if you parallel all the darlington transistors in one IC
it will sink 4 A ( check the maximum collector voltage also )
connect the common cathodes of the protection diode to the collectors
to the motor + supply

John