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1 Chapter Chapter Chapter Chapter 17 17 17 17 pnpn pnpn pnpn pnpn and Other Devices and Other Devices and Other Devices and Other Devices
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Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

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Page 1: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

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Chapter Chapter Chapter Chapter 17171717pnpnpnpnpnpnpnpn and Other Devicesand Other Devicesand Other Devicesand Other Devices

Page 2: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

pnpnpnpnpnpnpnpnpnpnpnpnpnpnpnpn DevicesDevicesDevicesDevicesDevicesDevicesDevicesDevices

SCRSCR——siliconsilicon--controlled rectifiercontrolled rectifierSCS SCS –– siliconsilicon--controlled switchcontrolled switch

GTO GTO –– gate turngate turn--off switchoff switchLASCR LASCR –– lightlight--aActivated SCRaActivated SCR

Shockley diodeShockley diodeDiacDiacTriacTriac

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

TriacTriac

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Page 3: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

SCRSCRSCRSCRSCRSCRSCRSCR————————SiliconSiliconSiliconSiliconSiliconSiliconSiliconSilicon--------Controlled RectifierControlled RectifierControlled RectifierControlled RectifierControlled RectifierControlled RectifierControlled RectifierControlled Rectifier

The SCR is a switching device for high-voltage and high-current operations.

Like an ordinary rectifier, an SCR conducts in one direction

The terminals are:

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

The terminals are:• Anode• Cathode• Gate

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Page 4: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

SCR OperationSCR OperationSCR OperationSCR OperationSCR OperationSCR OperationSCR OperationSCR Operation

To switch on an SCR:

• Forward bias the anode-cathode terminals (VF)

AND

• Apply sufficient gate

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

Once an SCR is switched on, it remains latched on, even when the gate signal is removed.

•• Holding currentHolding current (IH) is the minimum required current from anode to cathode

•• Reverse breakdown voltageReverse breakdown voltageis the maximum reverse bias voltage for the SCR

• Apply sufficient gate voltage (Vgate) and gate current (I GT)

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Page 5: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

To switch off an SCR:

• Remove the power source the anode and cathode terminals

OR

• Reverse bias the anode and

SCR OperationSCR OperationSCR OperationSCR OperationSCR OperationSCR OperationSCR OperationSCR Operation

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

• Reverse bias the anode and cathode terminals

An SCR cannot be switched off by simply removing the gate voltage.

Commutation circuitry can be used for satisfying either of the conditions for switching off an SCR.

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Page 6: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

Commutation Commutation circuitry is simply a class of switching devices connected in parallel with the SCR.

A control signal activates the switching circuitry and provides a low impedance bypass for the anode to cathode current. This momentary loss of current through

SCR CommutationSCR CommutationSCR CommutationSCR CommutationSCR CommutationSCR CommutationSCR CommutationSCR Commutation

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

This momentary loss of current through the SCR turns it off.

The switching circuitry can also apply a reverse bias voltage across the SCR, which also will turn off the SCR.

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Page 7: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

SCR False TriggeringSCR False TriggeringSCR False TriggeringSCR False TriggeringSCR False TriggeringSCR False TriggeringSCR False TriggeringSCR False Triggering

An SCR can be forced to trigger conduction under several conditions that must be avoided:

• Excessively high voltage from anode to cathode

• High frequency signal from gate to cathode

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

cathode• High operating temperature

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Page 8: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

The gate voltage can be set to fire the SCR at any point in the AC cycle.

SCR Phase ControlSCR Phase ControlSCR Phase ControlSCR Phase ControlSCR Phase ControlSCR Phase ControlSCR Phase ControlSCR Phase Control

In this example, the SCR fires as soon as the AC cycle crosses 0V. Therefore it acts like a half-wave rectifier.

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

like a half-wave rectifier.

In this example, the SCR fires later—at the 90°°°° point—on the positive half-cycle.

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Page 9: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

SCR ApplicationsSCR ApplicationsSCR ApplicationsSCR ApplicationsSCR ApplicationsSCR ApplicationsSCR ApplicationsSCR Applications

In these applications the SCR gate circuit is used to monitor a situation and trigger the SCR to turn on a portion of the circuit.

• Battery-charging regulator• Temperature controller circuit• Emergency-lighting system

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

• Emergency-lighting system

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Page 10: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

SCSSCSSCSSCSSCSSCSSCSSCS————————SiliconSiliconSiliconSiliconSiliconSiliconSiliconSilicon--------Controlled SwitchControlled SwitchControlled SwitchControlled SwitchControlled SwitchControlled SwitchControlled SwitchControlled Switch

An SCS is like an SCR, except that it has two gates: a cathode gate and an anode gate.

Either gate can fire the SCS• A positive pulse or voltage on the

cathode gate• A negative pulse or voltage on the anode

gate

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

gate

Either gate can switch off the SCS• A negative pulse or voltage on the

Cathode gate• A positive pulse or voltage on the anode

gate

Note: The anode gate requires higher voltages than the cathode gate.

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Page 11: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

SCSSCSSCSSCSSCSSCSSCSSCS

Comparison of the SCR and SCS:

• The SCS has a much lower power capability compared to the SCR

• The SCS has faster switching times than the SCR• The SCS can be switched off by gate control

ApplicationsApplicationsApplicationsApplicationsApplicationsApplicationsApplicationsApplications

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

ApplicationsApplicationsApplicationsApplicationsApplicationsApplicationsApplicationsApplications

• Pulse generator• Voltage sensor• Alarm circuits

Pin Identification

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Page 12: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

GTOGTOGTOGTOGTOGTOGTOGTO————————Gate TurnGate TurnGate TurnGate TurnGate TurnGate TurnGate TurnGate Turn--------Off SwitchOff SwitchOff SwitchOff SwitchOff SwitchOff SwitchOff SwitchOff Switch

GTOs are similar to SCRs, except that the gate can turn the GTO on and off.

It conducts only in one direction.

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

ApplicationsApplications

• Counters• Pulse generators• Oscillators• Voltage regulators

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Page 13: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

GTOGTOGTOGTOGTOGTOGTOGTO

Comparison of the GTO and SCS:

• GTO is a low power device• The gate signal necessary to fire the GTO is larger than the SCR gate signal.• The gate signal necessary to turn the GTO off is similar to that of SCS• The switching rate for turning the GTO off is much faster than the SCR

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Page 14: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

LASCRLASCRLASCRLASCRLASCRLASCRLASCRLASCR————————LightLightLightLightLightLightLightLight--------Activated SCRActivated SCRActivated SCRActivated SCRActivated SCRActivated SCRActivated SCRActivated SCR

The LASCR is an SCR that is fired by a light beam striking the gate-cathode junction or by applying a gate voltage.

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

ApplicationsApplications

• Optical light controls• Relays• Phase control• Motor control• Computer applications

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Page 15: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

Shockley DiodeShockley DiodeShockley DiodeShockley DiodeShockley DiodeShockley DiodeShockley DiodeShockley Diode

The Shockley diode conducts once the breakover voltage is reached. It only conducts in one direction.

OperationOperation

The Shockley diode must be forward biased, and then once the voltage reaches the breakover level it will conduct. Like an SCR it only conducts in one

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

will conduct. Like an SCR it only conducts in one direction.

ApplicationApplication

• Trigger switch for an SCR

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Page 16: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

DiacDiacDiacDiacDiacDiacDiacDiacThe Diac is a breakover type device.

OperationOperation

Once the breakover voltage is reached the Diac conducts. The Diac, though, can conduct in both directions. The breakover voltage is approximately symmetrical for a positive and a negative breakover voltage.

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

ApplicationsApplications

• Trigger circuit for the Triac• Proximity sensor circuit

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Page 17: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

A triac is like a diac with a gate terminal.

OperationOperation

When fired by the gate or by exceeding the breakover voltage, a triac conducts in both directions.

ApplicationsApplications

TriacTriacTriacTriacTriacTriacTriacTriac

Copyright ©2009 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458 • All rights reserved.

Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

Terminal IdentificationTerminal Identification

ApplicationsApplications

• AC power control circuits

more…more…

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Page 18: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

Triac Terminal IdentificationTriac Terminal IdentificationTriac Terminal IdentificationTriac Terminal IdentificationTriac Terminal IdentificationTriac Terminal IdentificationTriac Terminal IdentificationTriac Terminal Identification

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Page 19: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

The Unijunction Transistor (UJT)The Unijunction Transistor (UJT)The Unijunction Transistor (UJT)The Unijunction Transistor (UJT)The Unijunction Transistor (UJT)The Unijunction Transistor (UJT)The Unijunction Transistor (UJT)The Unijunction Transistor (UJT)

The unijunction transistor (UJT) has two base terminals (B1 and B2) and an emitter terminal (E).

The UJT symbol resembles the FET

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The UJT symbol resembles the FET symbol. The emitter terminal is angled as shown.

Page 20: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

The interbase resistanceinterbase resistance(RBB) is the total resistance between the two base terminals when IE = 0 A.

UJT Equivalent CircuitUJT Equivalent CircuitUJT Equivalent CircuitUJT Equivalent CircuitUJT Equivalent CircuitUJT Equivalent CircuitUJT Equivalent CircuitUJT Equivalent Circuit

The intrinsic standoff ratiointrinsic standoff ratio(η) is the ratio of RB1 to RBBwhen IE = 0 A.

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

2020

Conduction through the emitter terminal begins when the emitter voltage reaches the firing potential, given as

DBBP VηVV +=

Page 21: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

UJT Negative Resistance RegionUJT Negative Resistance RegionUJT Negative Resistance RegionUJT Negative Resistance RegionUJT Negative Resistance RegionUJT Negative Resistance RegionUJT Negative Resistance RegionUJT Negative Resistance Region

After a UJT fires, emitter voltage decreases as emitter current increases.

The negative resistance negative resistance

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The negative resistance negative resistance regionregion of operation is definced by the peak point (VP) and the valley point (VV).

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UJT Emitter CurvesUJT Emitter CurvesUJT Emitter CurvesUJT Emitter CurvesUJT Emitter CurvesUJT Emitter CurvesUJT Emitter CurvesUJT Emitter Curves

The UJT emitter curves show the effect of VBB on UJT firing voltage (VP).

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

2222

The higher the value of VBB, the higher the value of (VP) required to fire the component.

Page 23: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

Using a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCR

The UJT is commonly used as a triggering device for other breakover devices, like the SCR.

The SCR shown is triggered when the UJT emitter circuit conducts.

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

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conducts.

As the capacitor charges, VEincreases. When it reaches VP, the UJT fires. The voltage developed across R2 triggers the SCR.

Page 24: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

Using a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCRUsing a UJT to trigger an SCR

The VE and VR2 waveforms for the SCR triggering circuit (below) are shown.

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

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Page 25: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

The PhototransistorThe PhototransistorThe PhototransistorThe PhototransistorThe PhototransistorThe PhototransistorThe PhototransistorThe Phototransistor

The phototransistor is a light-controlled transistor. The current through the collector and emitter circuits is controlled by the light input at the base.

The collector current is the product of

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

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The collector current is the product of the transistor current gain (hfe) and the light induced base current (Iλ).

λfeC IhI =

Page 26: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

Phototransistor IC PackagePhototransistor IC PackagePhototransistor IC PackagePhototransistor IC PackagePhototransistor IC PackagePhototransistor IC PackagePhototransistor IC PackagePhototransistor IC Package

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Page 27: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

OptoOptoOptoOptoOptoOptoOptoOpto--------IsolatorsIsolatorsIsolatorsIsolatorsIsolatorsIsolatorsIsolatorsIsolators

PhotodiodePhotodiode

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

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PhotoPhoto--DarlingtonDarlington PhotoPhoto--SCRSCR

Page 28: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

PUTPUTPUTPUTPUTPUTPUTPUT————————Programmable UJTProgrammable UJTProgrammable UJTProgrammable UJTProgrammable UJTProgrammable UJTProgrammable UJTProgrammable UJT

Characteristics Characteristics

In some of its operating characteristics, a PUT is more like an SCR.

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

Like the UJT, the PUT has a negative resistance region. But this region is unstable in the PUT. The PUT is operated between the on and off states.

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Page 29: Chapter Chapter 17 117717 pnpn and Other Devices - KMUTTwebstaff.kmutt.ac.th/~suwat.pat/material/ene212 ch 17 pnpn.pdf · Chapter Chapter 17 117717 pnpn and Other Devices. pnpn Devices

Reducing or removing the gate voltage dies not turn off the PUT. Instead, like an SCR, the Anode to Cathode voltage must drop sufficiently to reduce the current below a holding level.

The gate voltage required to turn the

PUT FiringPUT FiringPUT FiringPUT FiringPUT FiringPUT FiringPUT FiringPUT Firing

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Electronic Devices and Circuit Theory, 10/eRobert L. Boylestad and Louis Nashelsky

PUT on is determined by external components, and not by specifications of the device as in the η value for the UJT.

BBBBB2B1

B1G ηVV

RRR

V ====++++

====

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