How to drive eight PIN diodes in parallel with 90 mA current using Arduino Uno R3

I am driving columns of eight PIN diodes, each in an array for a project. All of the columns are tied to a common ground. I expect the current of the parallel diodes to be approximately 90 mA (11 mA per diode x 8). See schematic below. I am using the Arduino Uno R3 as my digital controller. To my understanding, Arduino Uno R3's digital output pins can only handle 20 mA per pin. I need a solution to drive my digital signals with 90 mA current. I purchased ULN2003A High-Current Darlington Transistor Arrays ( I can light up LEDs using the ULN2003A, but I am confused about using it for my application. Since all 256 diodes (16 columns x 8) in my array are tied to a common ground, I'm not sure the ULN2003A is a workable solution. How do you recommend that I drive each 90 mA column without damaging my Arduino? Is there a workable solution using the ULN2003A?

My column schematic with 8 PIN diodes in parallel:

Example of UNL2003 with diodes: ULN2003 IC Pinout, Features, Equivalents & Datasheet

Are ALL the PIN diodes from the same wafer? How do insure they will all conduct identical currents and at the SAME time?

I don't think that I have a way to ensure all PIN diodes will conduct identical currents. How much of an issue is this?

My confusion is that I expected the current driver to be between V1 and R1, but FET switches seem to want to be between the diode and ground. I have seen papers that do what I am attempting to do, but I am unsure how to drive 90 mA.

The columns of diodes in my project are similar to what is shown below:

Clearly not.

But it gets worse - 16 groups!

I consider the ULN2x03 obsolete, you use the TPIC6B595 instead, but as you note, this can only source current.

You probably want a couple of UDN2983. Not very elegant, but should work.

Can you not have a resistor for each PIN diode?

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Thank you for the recommendation. I understand why it is better to place a resistor with each PIN diode. Still, I don't think it is possible for the electromagnetic surface I am building (similar to the graphic posted above). Each PIN diode is embedded in a reflecting metallic patch.

What is the application?
What is your project?

Thanks.. Tom... :smiley: :+1: :coffee: :australia:

It's an active reflector antenna. The PIN diodes function as phase-shifting switches.

If you are building the surface, can you not incorporate resistors into the surface?

In fact, is the surface grounded - could you not make the reference, the 5 V positive and connect the anodes of the diodes to that?

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