[sdiy] Transistor questions

[René Schmitz]

On 03.03.2025 06:16, David G Dixon via Synth-diy wrote:
> My question is this: given that the 2N390X transistors have higher 
> transition frequencies and lower collector capacitances than the old 
> Japanese transistors (according to All Transistors), why should the 
> latter give significantly faster saw reset times?  What is the actual 
> figure of merit for this?
>
This is not caused by the capacitances and inductivities alone.

There is a time required to remove all the charges in the base area when 
you turn it off. (mainly due to recombination IIRC)

This creates a turn off delay in a bipolar transistor called the storage 
time.


The question is how accurately this is modeled in simulations.


My preference for this style of VCO is to use switching transistors.

These have low Vce(sat) and are optimized for (drum roll) switching.


Best,

  René


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