Hello.
I'm trying to make an oscillator that would run from 200V range, providing about 1 kHz with minimal current drain.
I started with making a test one that would fit the parts i had on hand and to check the theory.
The transistors are ksp44, apparently with Vcesat=0.4V, Vbesat=0.75 and gain of 40 to 200.
Now, if i understand this right:
Ic=1mA
C=500pF
Rc=(V-Vcesat)/Ic=199KΩ
R=(V-Vbesat)/(Ic/gain)=19.925MΩ
f=1/(1.386*C*R)=72Hz
Thus, the rounded up result:
However, this circuit have two problems.
First, it oscillates at about 700Hz, not 72.
Second, it only peaks to 90V at collectors, not 190.
So, the question is - what did i do wrong?
Transistor's datasheet only lists ratings at 10V, can they be wildly different at 200V?
Secondary question - is there a better kind of oscillator to get 1kHz at 200V with less than 1mA of consumption?
With smaller capacitors needed for kHz range this kind of circuit stops working at all.