[sdiy] Transistor questions

[René Schmitz]

On 03.03.2025 20:56, David G Dixon wrote:
> The cap I'm using is 680pF, and it is discharging about 4V.
>
> According to my rough calculation, it would require a collector current of
> 1.36A to discharge that in 2ns, but only 0.136A to discharge it in 20ns.
> Hence, the 3904 could do it (with its maximum I_c of 0.2A) but the 945 could
> not (with its maximum I_c of only 0.1A).

You also need to stay within the allowed base current as one collector 
goes to the base of the other transistor.

Also the current splits across both possible paths, albeit with the 
extra diode in the way.


Cheers,

  René


-- 
--
synth at schmitzbits.de
http://schmitzbits.de