Firstly I apologise if this question is similar to another one I asked a while ago. But, as you will see, this is question is slightly different.
I have an amplifier which is a common emitter driving an AB push pull stage using MJE340/350 transistors.
I am using it to amplify a signal of 250kHz. The (unloaded) output voltage at 250kHz is 145.6 Vpp. This amplifier must be able to drive a signal for a time T.
I want to use it to drive a load with impedance Z = 669.2Ohms.
From V=IR, I can see that the current requirement is 0.21757 A. The power supplys I am using are R12-100B's which, from the data sheet, provide 50 mA each, So the total current provided is 100 mA (I added them because I am working with the peak to peak voltage, so both halves of the wave).
This leaves me with a current deficit of 0.1176 mA. To supply this excess current there are two capacitors. The value of the capacitors is 3.3 uF rated to take 450V. These are decoupling the supply rails which are at +/- 120 V. So essentially I have one 6.6uF capacitor charged to 240 V.
From Q = CV I know there are 0.001584 coulombs of charge stored. I also know that 1 Amp is defined as is 1 Coulomb of charge passing a point in 1 second. For this I can say that if A = C/s then C/A = s.
So to calculate the maximum time T which I can transmit this signal for I divide the amount of charge by the current deficit. This gives me a value of 13.47 mS which the signal can be transmitted for.
Now I know that as a capacitor discharges the voltage across the capacitor decreases so this method is not quite correct as this is not taken in to account.
So my questions are:
1) How much (if any) of my calculations are valid?
2) How should I take into account the voltage drop as the caps discharge (I assume I just a bigger value...)?
3) Should I use a few smaller caps because of the high frequency being used?
4) The voltage output was measured (using a pico scope with a probe on *10) with no load applied, will this value still be valid when the amplifier is loaded?