Mosfet instead of Q2 and Q3 bipolar ?

[pit34]

Hello,

I ask myself why does Q2 and Q3 are bipolar tranistor and not mosfet ? There is an explanation of operation here : https://wemakethings.net/2012/09/26/capacitance_measurement/ But not why bipolar instead of mosfet to discharge the capacitor.

Thanks

[kriskeillor]

Just a guess from me, but BJTs are cheaper and they do the same thing. That could be the reason.

[Miceuz]

Err, I don't remember exactly, but I think BJTs I had in my bin were faster to switch than mosfets I had. But in general I had to scrap the idea of discharging as it creates a lot of complication (switching transistor really fast is not simple) and does not give a lot of pros.