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Electronics Theory

How to Connect a Relay through an Opto-Coupler

Last Updated on May 20, 2026 by Swagatam 56 Comments

opto coupler relay driver circuit

In the following post I have explained how to drive a relay by using an isolated method, or through an optocoupler device. We will learn three methods, first method is by connecting relay directly with the optocoupler output pins, second method is by using external PNP transistors, and third method is by using external NPN […]

Filed Under: Electronics Theory Tagged With: Connect, Coupler, Opto, Relay, through

How to Generate PWM Using IC 555 (2 Methods Explored)

Last Updated on May 20, 2026 by Swagatam 93 Comments

oscillator 555 50 duty cycle 080261320

The IC 555 is an extremely useful and versatile device which can be applied for configuring many useful circuits in the field of electronics. One very useful feature of this IC is its ability to generate PWM pulses which can be dimensioned or processed as per the needs of the application or the circuit. What’s […]

Filed Under: Electronics Theory Tagged With: 555, Explored, Generate, Methods, PWM

Transistor Relay Driver Circuit with Formula and Calculations

Last Updated on May 20, 2026 by Swagatam 131 Comments

Relaydriver

In this article we will comprehensively study a transistor relay driver circuit and learn how to design its configuration by calculating the parameters through formulas. Importance of Relay Relays are one of the most important components in electronic circuits. Especially in circuits where high power transfer or mains AC load switching is involved, relays play […]

Filed Under: Electronics Theory Tagged With: Calculations, Driver, Formula, Relay, Transistor

How to Replace a Transistor (BJT) with a MOSFET

Last Updated on May 20, 2026 by Swagatam 77 Comments

pinout

In this post I have explained the method of correctly replacing a BJT with a MOSFET, without affecting the final outcome of the circuit. Introduction Until MOSFETs arrived in the field of electronics, transistors or BJTs to be precise ruled the power switching circuits and applications. Though even Bipolar Junction Transistors (BJTs) can not be […]

Filed Under: Electronics Theory Tagged With: BJT, MOSFET, Replace, Transistor

Understanding and Using a Piezo Transducer

Last Updated on May 20, 2026 by Swagatam 11 Comments

piezotransducerelement

In this post we try to investigate what transducers are and how they need to be configured in circuits while using them in a given application Understanding Piezo Transducers A piezo transducer is a device primarily used for converting an applied frequency to audible sound. It may be compared to a loud speaker, the only […]

Filed Under: Electronics Theory Tagged With: Piezo, Transducer, Understanding

Astable Multivibrator Circuit Using NAND Gates

Last Updated on May 20, 2026 by Swagatam 4 Comments

Astable Multivibrator Circuit Diagram Using IC 4093 NAND Gate2C Image

An astable multivibrator is referred to an electronic configuration which is able to generate continuous alternate high and low pulses from a couple of outputs, operating in tandem. Why IC 4093 You might have well come across such astable circuits using a couple of transistors, a couple of capacitors and a few resistors.However more simpler […]

Filed Under: Electronics Theory Tagged With: Astable, Gates, Multivibrator, NAND

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