Switching a low voltage to a load

Fibo · 2015-11-24T16:45:56+00:00

Hello, I want to switch a low voltage to a load. The voltage is 1.2V and it will be powering a .25A load. At first I though about a pmos transistor, but I do not have any negative rails available on my circuit, and I don't think pulling the gate to ground is a good enough Vgs. Can anyone recommend a simple way to pass 1.2V to my load with a digitally controlled switch? Much thanks!

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Jim Thompson 10 years ago

Poor voltage drop. ...Jim Thompson

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tabbypurr 10 years ago

All you need for a -ve rail is a small cap + diode connected to any node that switches. However this generally does mean the -ve rail doesn't go -ve until after Vcc is applied.

NT

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whit3rd 10 years ago

That's a mistake. Any substantial load should always be switched in/out at one of your power supply rails, because those allow easy biasing decisions: a 3.3V high-side switch is easy. A 0.0V low-side switch is easy. A 1.2V switch requires the ground current to get the same 0.25A modulation as a ground-side switch, but it's harder to bias a MOSFET to do it.

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legg 10 years ago

Should be less than 100mV, using jellybean (~BC807). Thats equivalent to a 400mR fet, without looking.

RL

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Jim Thompson 10 years ago

The OP, IIRC, said 0.5 AMP. ...Jim Thompson

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legg 10 years ago

See above - 0.25A

RL

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Switching a low voltage to a load

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