Diode Applications
LOAD-LINE ANALYSIS
The operating point (Q point)
The operating point or Q point of the diode is the
quiescent or no-signal condition. The Q point is
obtained graphically and is really only needed when
the applied voltage is very close to the diode’s
barrier potential voltage.
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Example
Solution
Series diode configurations with
DC inputs
Example 1
Example 2
Example 3
EXAMPLE 4
Vo  0.7
VR E  VD
I1 


R
R
10 V  0.7 V
0.33KΩ  28.18mA
EXAMPLE 5
V0  12  0.3  11 .7 V
EXAMPLE 6
V
0.7V
T
2
I1 

 0.212 mA
R
1 3.3KΩ
By KVL :
- V2  E  VT1  VT2  0
V2  E  VT1  VT2  20V  0.7V  0.7V  18.6V
V
18.6V
I2  2 
 3.32mA
R
5.6KΩ
2
I D 2  I 2  I1  3.32mA  0.212mA  3.108 mA
Diode Applications
• Rectifier
a device for converting alternating AC
current into direct current DC
• Half-Wave Rectifier
• Full-Wave Rectifier
SINUSODIAL INPUT
HALF-WAVE RECTIFICATION
Half-Wave Rectifier
Vdc  0.318Vm
Vdc  0.318(Vm  VT )
Effect of VT on half-wave rectified signal
The peak Inverse voltage PIV
for half wave rectifier
Determining the required PIV ratting for the half wave
rectifier
PIVrating  Vm
Bridge Rectifier
Full – wave rectification
Bridge Rectifier
Vdc (average voltage):
for ideal diodes and
for silicon diodes
Determining the required PIV ratting for the
bridge configuration
PIV  Vm
Full – wave rectification
Center tapped transformer
Full – wave rectification
Center tapped transformer
Full – wave rectification
Center tapped transformer
• Determine PIV (PRV) for each diode:
Inserting the maximum voltage for the secondary voltage and Vm as
established by the adjoining loop will result in
PIV = Vsecondary + VR
=
Vm
PIV ≥ 2 Vm
+ Vm