2 diode applications

2.0 Diode Applications 1 of 31 2.1 Introduction 2.2 Load-Line Analysis

2.0 Diode Applications 2 of 31 Drawing the load line and finding the point of operation. Drawing the load line. 1) Redraw the circuit with the diode on the right. 2) Remove the diode and find a couple of points on the curve of VD vs. ID. Convenient points are, the current when VD = 0 and the voltage when ID = 0. Draw the line connecting these two points and note the voltage on the horizontal axis.

Note the intersection point.

VRVD

2.0 Diode Applications 3 of 31 Example 2.1

VD = 0.7

2.0 Diode Applications 4 of 31 2.3 Diode Approximations Series Diode Configurations with DC Inputs (a) Circuit; (b) characteristics

Silicon 0.7 Germanium 0.3

Series Diode Configurations. Circuit for Example 2.11.

2.0 Diode Applications 5 of 31 2.5 Parallel and Series-Parallel Configuations Two diodes sharing the load current.

2.0 Diode Applications 6 of 31 Network for Example 2.15.

2.0 Diode Applications 7 of 31 2.6 AND/OR Gates OR gate

2.0 Diode Applications 8 of 31 AND Gate

2.0 Diode Applications 9 of 31 2.7 Sinusoidal Inputs: Half-Wave Rectification

Conduction region (0→T/2).

2.0 Diode Applications 10 of 31 Average voltage output

Vavg ≈ 0.318(Vm - VT ) Effect of VT on half-wave rectified signal. Silicon diode, VT = 0.7 Vavg ≈ 0.318(Vm - VT )

2.0 Diode Applications 11 of 31 2.8 Full-Wave Recification

2.0 Diode Applications 12 of 31 Conduction path for the positive region of vi.

Conduction path for the negative region of vi.

Input and output waveforms for a full-wave rectifier.

Vavg ≈ 0.636Vm Vavg ≈ 0.636(Vm - VT )

2.0 Diode Applications 13 of 31 Center-tapped transformer full-wave rectifier.

Network conditions for the positive region of vi.

2.0 Diode Applications 14 of 31 Network conditions for the negative region of vi.

2.0 Diode Applications 15 of 31 Bridge network for Example 2.19.

2.0 Diode Applications 16 of 31 Network of Fig. 2-65 for the positive region of vi.

2.0 Diode Applications 17 of 31 Redrawn network of Fig. 2-66.

2.0 Diode Applications 18 of 31 2.9 Clipper

2.0 Diode Applications 19 of 31 Series clipper with a dc supply.

2.0 Diode Applications 20 of 31 Example 2.20

2.0 Diode Applications 21 of 31 Response to a parallel clipper.

2.0 Diode Applications 22 of 31 Example 2.22.

2.0 Diode Applications 23 of 31 2.9 Clamp

2.0 Diode Applications 24 of 31 Applied signal and network for Example 2.24.

2.0 Diode Applications 25 of 31 2.11 Zener Diode

2.0 Diode Applications 26 of 31 Example 2.26

2.0 Diode Applications 27 of 31

The output voltage across the Zener is Vz.The minimum value of RLmin is given by the equation,

Vz Vi RLminR RLmin.R RLmin

Vi RLminRLmin

RLmin RVzVi Vz.VzVi Vz

Now to find the maximum value of RL. As the value of RL isincreased the current through the Zener is increased.

Izm IR IRLminIR IRLmin

IRLmin VzRLmax

VzRLmax

Izm IR VzRLmax

IR VzRLmax

RLmax VzIR Izm

VzIR Izm

RLmax VzVi Vz

RIzm

RIzm

VzVi Vz Izm

2.0 Diode Applications 28 of 31 2.12 Voltage-Multiplier Circuits Voltage Doubler

Half-wave doubler

2.0 Diode Applications 29 of 31 Voltage Tripler

2.0 Diode Applications 30 of 31 2.13Practical Applications Inductor bypass with diode

2.0 Diode Applications 31 of 31 Protection using diodes Battery backup Polarity detector Voltage reference levels AC regulator & square-wave generator