[sdiy] Signals leaking into the PSU?

[René Schmitz]

On 24.02.2023 12:16, Neil Johnson via Synth-diy wrote:
> Hi Scott,
>
>> Here's a way to keep a constant current driving a flashing LED using a differential pair.  It only takes one extra resistor and transistor compared to the standard transistor
>> I whipped up a page for it:
>> https://www.bernacomp.com/elec/og2/constant_current_led.html
> Thanks - an interesting solution.  My only concern would be driving it
> from 0V to 5V.  At 0V both bases are at the same voltage so the
> current will split between the two transistors depending on their
> matching.  If they were both perfectly matched then the current would
> split equally between the two paths, so the LED would see half of the
> "on" current.

Lift the base of the other transistor to 2.5V or something.


Best,

  René

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