# Post-Transformer RMS Voltage for This Circuit?

I am confused here. For the below circuit: simulate this circuit – Schematic created using CircuitLab

Ripple voltage is given as 1V peak to peak, Vo = 15V DC. I have assumed a 0.7V drop across any given diode. Please note that I was a little hasty in my construction. I do not know the values of the capacitors or resistors yet. The transformer line has 60 Hz frequency.

I'm trying to find the transformer rms voltage to the circuit where the turns of the transformer are not known.

I calculated: 2*16V + 1.4V, since there are two diode drops, the center tap configuration giving two instances of the maximum load voltage, which is 15V + 1V ripple. This gives 33.4V, which, dividing by sqrt(2) for rms gives about 23.6V (rms). However, the given answer is 22.9V (rms)

What am I missing in my calculation? Any clarification would be greatly appreciated!

• Try 2*15.5+1.4. Ripple goes up and down. – Marquis of Lorne Jun 6 '13 at 19:29
• Ahh my God! Of course! A peak to peak ripple of 1V is +/- 0.5V. Thanks, I feel stupid for having missed it, but I really appreciate you pointing it out! – Rome_Leader Jun 6 '13 at 19:29
• I Think you're missing a ground at the midpoint of the two capacitors. – Connor Wolf Jun 6 '13 at 20:13