# FACULTY OF ELECTRICAL ENGINEERING UNIVERSITI TEKNOLOGI MARA PRINCIPLES OF APPLIED ELECTRONICS

### FACULTY OF ELECTRICAL ENGINEERING UNIVERSITI TEKNOLOGI MARA PRINCIPLES OF APPLIED ELECTRONICS

FACULTY OF ELECTRICAL ENGINEERING
UNIVERSITI TEKNOLOGI MARA
PRINCIPLES OF APPLIED ELECTRONICS
(ELE526)
MINIPROJECT

TOC o “1-3” h z u OBJECTIVE PAGEREF _Toc529648909 h 4INTRODUCTION PAGEREF _Toc529648910 h 5Non-inverting Schmitt Trigger PAGEREF _Toc529648911 h 6Inverting Schmitt Trigger PAGEREF _Toc529648912 h 7METHODOLOGY PAGEREF _Toc529648913 h 8a)Theoretical Calculation PAGEREF _Toc529648914 h 8b)Computer Simulation PAGEREF _Toc529648915 h 8RESULTS & DISCUSSION 20% PAGEREF _Toc529648916 h 9CONCLUSION & RECOMMENDATIONS 10% PAGEREF _Toc529648917 h 10

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OBJECTIVE
The students will integrate all the knowledge gained so far in theory and computer software applications through the actual realization in the form of a mini project.
TITLE Schmitt trigger switch
SPECIFICATION
Design and evaluate:
I. An inverting Schmitt trigger so that VUTP = – 8V and VLTP = – 4V. Assume Vsat = ± 12 V.
II. A noninverting Schmitt trigger so that VUTP = 8V and VLTP = 4V. Assume Vsat = ± 12 V.

INTRODUCTION
In electronics system, a Schmitt trigger is a comparator circuit with hysteresis positive feedback to the non-inverting input differential amplifier. It is active circuit that converts an analog input signal to a digital output signal. The circuit is named a “trigger” because the output retains its value until the input changes sufficiently to trigger a change. In the non-inverting, when the input is higher than a chosen threshold, the output is high. When the input is lower threshold the output is low, and when the input between two levels the output remain the same value. This threshold action called hysteresis. There is close relation between the two circuits: a Schmitt trigger can converted into a latch and vice versa.
Schmitt trigger devices are used in signal conditioning applications to remove noise from signals used in digital circuits. They are also used in closed loop negative feedback configurations to implement relaxation oscillators, used in function generators and switching power supplies.

29789617600 This diagram shows transfer function of a Schmitt trigger. The horizontal and vertical axes are input voltage and output voltage, respectively.

Non-inverting Schmitt Trigger
Schmitt trigger by a non-inverting Schmitt trigger
The resistors R1 and R2 form a parallel voltage summer and it adds a part of the output voltage to the input voltage during and after switching that occurs when the resulting voltage is near ground. This parallel positive feedback create hysteresis that is controlled between the resistances of R1 and R2. The output is single-ended and produces voltage to ground so the circuit does not need an amplifier. Since conventional op-amps have different input, the inverting input is grounded to make the reference point zero volts.

If the Schmitt trigger in the high state, the output be at the positive power supply (+VS). The output voltage V+ of the resistive summer can be found by applying the superposition theorem:
V+=R2R1+R2.Vin+R1R1+R2.Vs
Inverting Schmitt Trigger
METHODOLOGY
Theoretical Calculation
Computer Simulation

RESULTS & DISCUSSION 20%
CONCLUSION & RECOMMENDATIONS 10%

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