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can you draw a circuit you have in mind? I'm pretty sure you can use a MOSFET to do this, but to give you a precise answer I'd need to understand it better
hey electronics twitter what's the easiest way to control (not just on/off, but analog control) a ~3.3V LED from my ~3.3V microcontroller, using a ~4V signal. a transistor doesn't seem to work bc the voltage drop results in emitter voltage being ~3.3V-0.7V=2.6V which is too low
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how exactly do MOSFETs differ from NPN transistors that helps me here
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Is there a reason you can't PWM the LED based on an ADC of the 4V input (later probably will need a resistor divider)? Assuming it's for brightness control
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if i use a transistor to control the signal, the voltages look as follows: base voltage: ~3.3V emitter voltage: ~2.6V <--- TOO LOW!!! because the emitter voltage is limited by the base
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LED anode to 3.3v, catode to Drain, source to Ground, microcontroller pin doing PWM to Gate, Gate to Ground through a 100k resistor.
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if pwm control is acceptable, there might be a mosfet with an acceptable threshold voltage that works
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i think i misunderstood, the other posters comment of a voltage divided adc controlling a pwm output would would work if pwm is acceptable
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What is generating the 4V "signal"? I'm assuming you can't put the LED on 5V, and your concern is not being able to turn on the MOSFET hard enough? Are BJTs or PMOS a possibility? There are gate driver ICs and things like charge pumps, though I've never needed to use one.
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I can send over a few FETs I use tomorrow, they may be of use!
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