Diode circuit with AC excitation source

4 replies · 2K views · last reply
Gbox
Messages
54
Reaction score
0

Homework Statement


Graph ##V_{out}##
Hand-drawn circuit schematic with a source Vin, series capacitor C1, a diode with shunt capacitor C2, and a second diode across the output terminals labelled Vout, beside a graph of Vin against t that alternates between V and -V as a square wave.


Homework Equations

The Attempt at a Solution



When ##V_{in}=V## C1 is positive on the left and negative on the right, and C2 is negative on the the down side and positive on the upper side so there is no Vout?
 
Gbox said:
When Vin=VVin=VV_{in}=V C1 is positive on the left and negative on the right, and C2 is negative on the the down side and positive on the upper side so there is no Vout?

That's not correct.

For the moment let's assume that V is much greater than the forward voltage of the diode...

When Vin = +V the right hand diode is reverse biased (not conducting) so that can be temporarily removed. The left hand diode is forward biased (conducting) so replace it with a wire. Redraw the circuit to show this.

Then... Are you familiar with the "Potential Divider" circuit?
 
CWatters said:
That's not correct.

For the moment let's assume that V is much greater than the forward voltage of the diode...

When Vin = +V the right hand diode is reverse biased (not conducting) so that can be temporarily removed. The left hand diode is forward biased (conducting) so replace it with a wire. Redraw the circuit to show this.

Then... Are you familiar with the "Potential Divider" circuit?
Why is the left hand diode is conducting? the capacitors do not affect the voltage? do not they both charge to the same voltage and the diode is not conducting?
 
No they don't charge to the same voltage (unless they are same value). The two caps are in series.
 
This is what the circuit looks like when Vin transitions from 0 to +V (assuming +V >> Vd)...

Circuit schematic: a voltage source labelled +V on the left feeds a series capacitor C1, with capacitor C2 connected in shunt from the junction down to the bottom rail.