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I've got some common anode 7 Segment displays that I want to use a Maxim 7219 IC to drive with. The Max7219 is designed for direct driving common cathode displays but Maxim do have an app note that describes using the chip to drive higher current and/or voltage 7 segment displays as long as they are in a common anode configuration. In my case I want common anode, but at regular voltage/current levels.

The led's are fairly typical, 25mA max current, 3.3Vf, and I intend to drive everything from a 5V supply voltage.

I am not really sure what I should be looking for in the transistors though? I went for these two

2n3904 NPN Datasheet

AO3401A Fet Datasheet

as they seem to be able to handle the relatively small currents and voltages involved, and seemed to be quite cheap. My proposed circuit is below. Does this seem like a good choice? Propopsed circuit

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  • \$\begingroup\$ I'd go for a constant current-sink segment drive on your low side. You've easily got enough headroom for it and it isn't expensive. Something along these lines. \$\endgroup\$ – jonk May 4 at 1:52
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You did select a proper MOSFET and NPN transistor for your application. You selected a MOSFET that could handle maximum current through each seven segment display ( with good headroom) and voltage rating. You selected a proper NPN transistor which can handle current of each LED and with proper voltage ratings. These transistors can work at 5V. The circuit also looks good.

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