Elektronika(TKE 4012)

Eka Maulana

maulana.lecture.ub.ac.id

Dioda-Dioda Khusus

(Special Purpose)

Pokok Bahasan

• Dioda Zener

• Dioda Zener - Regulator

• Dioda Zener Pendekatan kedua

• LED (Light Emitting Diode)

• Devais Optoelektronik

• Dioda Scottky

• Dioda Varactor

• Jenis Dioda Lain(Varistor, current-regulator, Step Recovery, Back diode, Tunnel Diode)

Rangkaian Dioda

0-2-4-6

-20

-40

-60

-80

-100

-120

-140

VZ (Volts)

I Z(m

A)

VZ

Kurva Karakteristik V-I Zener

Zener dioperasikan pada daerah breakdown saat dioda dibias mundur

Power

supplyVZ

VS

RS

RL

Voltage Regulator – Dioda Zener

Ketika tegangan thevenin yang menghadap dioda zener lebih besar dari pada

tegangan zener, maka rangkaian bersungsi sebagai regulator tegangan.

VTH =RL

RS + RL

VS

Power

supplyVZ

VS

RS

RL

IS =VS - VZ

RS

:: Zener conducting:

IL =VZ

RL

IZ = IS - IL

Voltage Regulator – Dioda Zener

Power

supply

R

RL

Dioda Zener – Rangkaian Waveshaping

VZ + 0.7 V

-VZ - 0.7 V

RZ

VZ

Dioda ZenerPendekatan Kedua

Power

supply

VS

RS

RL

RZ

VZ

Penerapan Zener Pendekatan Kedua

Deviasi tegangan beban dari kasus ideal:

DVL = IZRZ

Power

supply

VR(in)

RS

RL

RZ

VZ

Regulator Zener juga mengurangi Ripple Tegangan

Asusmsikan RL dan RS >> RZ:

VR(out) @ RZ

RS

VR(in)

Zener diode ratings

• Maximum power = PZ(max) = VZIZ(max)

• Available tolerances: 20, 10 and 5 percent

• Zener resistance, RZT, increases at the knee

of the characteristic curve

• A derating factor such as 3.2 mW per

degree for temperatures above 50 degrees

Celsius is typical.

0-10-20-30

-10

-20

-30

mA

V

RS

VS

Q1

Q2

1 kW

ketika VS divariasikan antara 20-30 volts, maka didapatkan VZ dengan:

Solusi Grafik - Load line

VS = 20 V-30 V

Load Line

Power

supply

VS

RS

Voltage drop LED (tipical) = 1,5 – 2,5 volt

LED

IS =VS - VD

RS

LED (Light Emitting Diode)

Power

supply

VS

RS

Photodioda berkerja pada reverse biasdan aktif (menghantar) jika dipicu cahaya

Photodioda

Photodioda

Signal

sourceV1

R1

Optocoupler : kombinasi LED and photodioda.

Power

supply

R2

V2

Optocoupler

Vin Vout

Vin

Vout

High-frequency rectification

Pada frekuensi tinggi,

penyimpanan muatan dapat

menyebabkan performansi yang rendah

Tails

Vin Vout

Vin

Vout

Hot-carrier rectifier

Schottky diodes eliminate

tails at high frequencies.

Less reverse bias

(more capacitance)

More reverse bias

(less capacitance)

Varactor symbol

A varistor diode can be used to protect

line-operated equipment from voltage surges.

Power

supply

VS

RS

Current-regulator diode

RS can vary over a wide range and the current stays the same.

Other diode types

• Laser: emits coherent light

• Step-recovery: snaps off when reverse

biased

• Back: conducts better when reverse

biased

• Tunnel: has a negative resistance region

Other diode applications

• Laser: CD players, communications

• Step-recovery: Frequency multipliers

• Back: Small-signal rectifiers

• Tunnel: High-frequency oscillators

Special Purpose Devices

Tugas

• Buat Rangkuman devais dioda-dioda khusus.

(konsep dasar, fungsi dan aplikasinya)