Theory and Operation of Programmable Unijunction Transistors (PUTs)

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Questions and Answers

What is the advantage of using PUT over UJT for pulse triggering?

PUT is more reliable and has a higher power handling capability.

What is the range of delay angle control of the SCR?

25° to 180°

What is Vz in the given context?

The Zener voltage

What is the purpose of controlling the delay angle of the SCR?

To regulate the firing angle of the thyristor and control the load. Signup and view all the answers

What is the significance of the delay angle in SCR triggering?

It controls the firing angle of the thyristor. Signup and view all the answers

What is the role of PUT in pulse triggering?

To generate a pulse to trigger the SCR. Signup and view all the answers

Why is PUT preferred over UJT for pulse triggering?

PUT is more reliable and has higher power handling capability. Signup and view all the answers

What is the purpose of designing a pulse triggering circuit for the SCR?

To control the load connected to the SCR. Signup and view all the answers

What is the relationship between the delay angle and the firing angle of the thyristor?

The delay angle determines the firing angle of the thyristor. Signup and view all the answers

What is the significance of Vz in designing the pulse triggering circuit?

It determines the Zener voltage. Signup and view all the answers

What is the primary application of PUT in SCR triggering?

Pulse triggering Signup and view all the answers

What is the range of delay angle control required in the given SCR circuit?

25° to 180° Signup and view all the answers

What is the purpose of controlling the delay angle in SCR triggering?

To control the firing of the SCR Signup and view all the answers

What is the significance of Vz in the SCR circuit design?

It is a critical circuit parameter Signup and view all the answers

What is the advantage of using a PUT over a UJT in SCR triggering?

It provides better pulse triggering capabilities Signup and view all the answers

How does the delay angle control affect the SCR's firing?

It determines the point at which the SCR fires Signup and view all the answers

What is the role of Vz in determining the SCR's firing angle?

It is a critical parameter in determining the firing angle Signup and view all the answers

Why is precise control over the delay angle necessary in SCR triggering?

To ensure proper firing of the SCR Signup and view all the answers

What is the significance of designing a pulse triggering circuit for the SCR?

It enables precise control over the SCR's firing Signup and view all the answers

Study Notes

Theory and Operation of PUTs

A PUT (Programmable Unijunction Transistor) has the same characteristics as a standard UJT.
The cathode (B1) is the reference terminal relative to which other voltages are measured.
The anode (E) voltage rises until it reaches a certain critical value called the peak voltage (VP) which causes the device to fire.
The peak voltage (VP) is determined by the external circuitry, unlike a UJT where VP is determined by the intrinsic standoff ratio associated with the transistor itself.
The gate (B2) receives a voltage from an external circuit.

PUT Relaxation Oscillator

The oscillation frequency is adjusted by varying the dc voltage applied to the gate from the RG1- RG2 voltage divider.
A PUT can be used in applications that need low supply voltage.

PUT for Triggering SCR

PUTs are used for triggering SCRs due to their ability to be programmed via gate voltage.

PUT Construction Slop Ramp Generator

The output ramps always maintain a constant slope, but the height of the ramps can be adjusted by programming the PUT via gate voltage VG.
This circuit could be used to furnish the input signal to an industrial servomechanism.

Advantages of PUT over UJT

The advantage of using PUT over UJT for pulse triggering is that the peak voltage (VP) can be controlled by external circuitry.

Application of Slop Ramp Generator

The voltage ramp furnishes the set-point signal to the servo system, increasing the ramp height would coincide with increasing the mechanism's stroke distance.

SCR Triggering Pulse Parameters

The SCR triggering pulse should have an amplitude of 15 V and a duration of 30 µsec.

PUT Parameters

Vs = 25 V and Ig = 0.5 mA are the parameters of the Programmable Unijunction Transistor (PUT).

PUT Application

PUT is used in applications that require a low supply voltage.

PUT Triggering Circuit for SCR

A PUT can be used to trigger an SCR.

PUT Construction and Slope Ramp Generator

The output ramps of a PUT always maintain a constant slope.
The height of the ramps can be adjusted by programming the PUT via gate voltage VG.

Applications of Slope Ramp Generator

Such a circuit can be used to furnish the input signal to an industrial servomechanism.
The voltage ramp can be used to provide a set-point signal to the servo system.
The ramp height is directly proportional to the mechanism's stroke distance.

Advantage of PUT over UJT for Pulse Triggering

The advantage of using PUT over UJT for pulse triggering is not explicitly stated in the text, but it is implied that PUT is more suitable for certain applications.

Delay Angle Control of SCR

To control the delay angle of the SCR in the range from 25° to 180°, Vz and all circuit parameters need to be found.
Vz and circuit parameters are not provided in the text, but can be calculated based on the specific application.

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Description

This quiz covers the theory and operation of Programmable Unijunction Transistors (PUTs), including their characteristics, firing, and applications in relaxation oscillators, thyristor firing, pulse circuits, and timing circuits.