### Author Topic: How can I build a 120v ac voltage source with a maximum output current of 5mA?  (Read 426 times)

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#### AMWallace123

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##### How can I build a 120v ac voltage source with a maximum output current of 5mA?
« on: January 31, 2018, 09:24:53 am »
Im working on a project that requires a 120v ac voltage source with a maximum output current of 5mA. What type of circuit or component can i use to accomplish this?  Thanks your help

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##### Re: How can I build a 120v ac voltage source with a maximum output current of 5mA?
« Reply #1 on: January 31, 2018, 10:59:57 am »
Love Cypress PSOC, ATTiny, Bit Slice, OpAmps, Oscilloscopes, and Analog Gurus like Pease, Miller, Widlar, Dobkin, obsessed with being an engineer

#### Cliff Matthews

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##### Re: How can I build a 120v ac voltage source with a maximum output current of 5mA?
« Reply #2 on: January 31, 2018, 03:25:54 pm »
That's quite a small current without details on usage, safety requirements, tightness of regulation and AC frequency. So assuming economy and 50/60Hz (not frequencies far beyond), one could back-to-back couple two <100ma wall-warts with some current limiting PTC's between. I'm not big on math and often prefer quick mock-ups, so let's leave it open for others to comment. Almost forgot, welcome to the forum!

#### Zero999

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##### Re: How can I build a 120v ac voltage source with a maximum output current of 5mA?
« Reply #3 on: January 31, 2018, 09:30:47 pm »
You forgot to say what your input voltage is.

If it's 120VAC, then all that's needed is a capacitor or resistor, to give the correct impedance, to limit the current to 5mA.

If it's 240VAC, then use two resistors or capacitors of the same value and correct impedance to limit the current to 5mA.

If it's DC, then you need an oscillator and amplifier to drive a transformer to get the correct voltage. Current limiting can be implemented in the amplifier's output stage.

Smf