Hi
My name is Jay, I am new to electronics and have stumbled across a problem regarding the ULN2003 Darlington driver IC. Usually this IC is used to sink current, therefore lighting a bulb or relay that is connected to the supply voltage.
However my question is:
Can the ULN2003 switch a PNP power transistor, so that it could provide a current source??
I have provided a drawing of my setup, and gave you it in writing below:
From what I have read this should be possible by connecting the transistor in the following manner:
- PNP base to output of ULN2003.
- PNP collector will be the current source, such as driving a bulb, a 1ohm resistor is also tied to ground from the collector.
- PNP emitter to positive supply rail.
- Resistor from PNP base to positive supply rail, to ensure transistor is switched off.
PNP transistors are turned on by negative voltage to base, the ULN2003 should do this. However it doesnt, and I am very confused by this!
Here is some more info about my setup:
- PNP transistor I have been experimenting with is the D45H8 power transistor (10A).
- Output of PNP goes to a 20W, 12V halogen bulb.
- Supply voltage to PNP = 12V.
- ULN2003 input voltage = 12V.
- Resistor from PNP base to supply rail = 100K.
- Pin 8 of ULN2003 connected to 0V
- Pin 9 of ULN2003 connected to supply rail = 12V
Thankyou
Jay
My name is Jay, I am new to electronics and have stumbled across a problem regarding the ULN2003 Darlington driver IC. Usually this IC is used to sink current, therefore lighting a bulb or relay that is connected to the supply voltage.
However my question is:
Can the ULN2003 switch a PNP power transistor, so that it could provide a current source??
I have provided a drawing of my setup, and gave you it in writing below:
From what I have read this should be possible by connecting the transistor in the following manner:
- PNP base to output of ULN2003.
- PNP collector will be the current source, such as driving a bulb, a 1ohm resistor is also tied to ground from the collector.
- PNP emitter to positive supply rail.
- Resistor from PNP base to positive supply rail, to ensure transistor is switched off.
PNP transistors are turned on by negative voltage to base, the ULN2003 should do this. However it doesnt, and I am very confused by this!
Here is some more info about my setup:
- PNP transistor I have been experimenting with is the D45H8 power transistor (10A).
- Output of PNP goes to a 20W, 12V halogen bulb.
- Supply voltage to PNP = 12V.
- ULN2003 input voltage = 12V.
- Resistor from PNP base to supply rail = 100K.
- Pin 8 of ULN2003 connected to 0V
- Pin 9 of ULN2003 connected to supply rail = 12V
Thankyou
Jay
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