1. PN junction diodes

2. PN Junction Diode
Allows current to flow in one direction but not the other
The anode connects to the p-type material, the cathode to the n-type material of the diode.

3. Forward Biased Diodes
The component is biased so that the anode is more positive than the cathode.
The diode conducts fully when VF is approximately
0.7 V (for silicon) or 0.3 V (for germanium).
The value of IF depends on the circuit voltage and resistance values.

4. Reverse Biased Diodes
The component is biased so that the cathode is more positive than the anode.
The voltage across the diode is approximately equal to the applied voltage (V ).
The diode current is approximately 0 A (as indicated by the ammeter).

5. Ideal diode characteristics
When forward biased (closed switch), the diode:
Has no resistance.
Does not limit current.
Has no voltage drop across its terminals.
When reverse biased (open switch), the diode:
Has infinite resistance.
Blocks current.
Drops the applied voltage across its terminals.

6. Current through Ideal diode
I = 10 mA
I = 0 mA

7. Characteristics of Junction diode
Forward-bias region
# Cut-in voltage - below which, minimal current flows
- approximately 0.5V
# Fully conducting region – region where Rdiode is approximately equal zero
between 0.6 and 0.8V
Diode current,

8. Characteristics of Junction diode
Reverse-bias region
# Saturation current- constant current in reverse direction
i = - Is
# Breakdown – when
VD << 0

9. Exponential Model most difficult to employ in circuit analysis
due to nonlinear nature
solve for ID in the circuit
VDD = 5V
R = 1 kOhm
ID = 1 0.7V
Solution…
graphical method

10. Graphical Analysis Using Exponential Model
load line and diode characteristic intersect at operating point

11. Diode Temperature dependence
The forward voltage drop decrease by approx. 2 mV for every 1°C increase in temperature
The reverse saturation current Is will double in magnitude for every 10°C increase in temperature

12. Diode Resistance
DC or Static Resistance
RD = VD/ID

13. Diode Resistance
AC or Dynamic Resistance

14. Diode Resistance Determining AC or Dynamic Resistance rd = ηVT ID
At room temperature
VT = 26 mV
rd = 26mV / ID

15. i-v relationship ID = Is (eVD/ηVT - 1)
Current I1 corresponding to diode voltage V1
I1 = Is (eV1/ηVT)
Current I2 corresponding to diode voltage V2
I2 = Is (eV2/ηVT)
I2/I1 = eV2 –V1/ηVT
V2 –V1 = ηVT ln(I2/I1)
V2 –V1 = 2.3ηVT log(I2/I1)

16. Diode Specifications Forward voltage Vf Maximum forward current If
Reverse saturation current
Reverse voltage
Peak Repetitive Reverse Voltage VRRM (or)
Peak Inverse Voltage PIV
Maximum power dissipation
Capacitance levels
Operating temperature range

17. Diode Specifications Peak Repetitive Reverse Voltage VRRM
VRRM is the maximum reverse voltage that a diode can withstand.
When VR > VRRM , diode reverse current (IR) increases rapidly as the depletion layer breaks down.
Average Forward Current (IF ) – The maximum allowable value of dc forward current for a diode.
Forward Power Dissipation ( PD(max) ) – The maximum possible power dissipation of the forward-biased diode.

18. Diode Specification Sheets

19. Diode Specification Sheets

20. Types of Diodes

21. Diode Testing

22. Diode Testing

23. Diode Applications

24. Diode Application

25. Diode Application

26. Clippers and Clampers

27. Diode Clippers
A clipper (or limiter) is a circuit used to eliminate some portion (or portions) of a waveform.
A series clipper is in series with its load.
A shunt clipper is in parallel with its load.

28. Series Clippers

29. Series Biased Clippers

30. Biased Shunt Clippers

31. Clampers

32. Clampers

33. Voltage Doublers
A voltage doubler provides an output that is twice its peak input voltage.

34. Voltage Doublers