That's a little tighter math than the PM I did with The Dodger because I neglected the Ib term in the collector current...because it is less than 1% of Ic. Another habit from designing 1% meters. I neglect things that are less than 1/2% until I'm doing the error budget calculations. In this circuit, the errors are a lot more about diminished Hfe at low Vc than it is about the base current being part of the collector resistor current.Have a look at the section "Collector Feedback Biasing a Transistor
Hi,View attachment 123697
Trying to find out how to calculate the resistors R2, R3, and seen this type of circuit used several times in electret mic preamps, and why they use it?...
Do you mean Gx=R2/R3??Hi,
To make this really short, if you calculate the initial gain as Gx=R3/R2 (which is really what we did above) then that's the very rough estimate, and the correction is then:
G=Gx*B*R3/(B*R3+R3+Gx*R1)
where G is the actual gain and B is the transistor Beta.
In the limit as B gets very high which is the initial rough assumption, G=Gx.
Do you mean Gx=R2/R3??
This would be 100K /10K =10...
Thanks, can you do a model for R2 from 470K to 2M2, so i can see what happens...