Electronics - Designing Filter Circuits

Authors Avatar

DEN 109 Electrical Technology                

DEN 109 Electrical Technology

Lab Experiment 1: Designing Filter Circuits

By Ali Asghari

DEN 109 Electrical Technology

Lab Experiment 1: Designing Filter Circuits

Introduction

The aim of this laboratory experiment was to devise a filter circuits using passive element which consisted of resistors and capacitors. In the experiment we had to design an active filter using operational amplifiers and operational amplifier elements. The filters had different acceptability range of frequencies. The filters are an electronic circuit which performs signal processing which intends to remove undesired signals to and from components but the filter will encourage the desired signals.

Filters are used in communication systems to pass those frequencies containing the desired information and to reject the remaining frequencies which are not within the range we are looking for. In stereo systems, for example, filters can be used to separate a particular band of frequencies for increased or decreased emphasis by the output acoustical system such as amplifier, speaker, etc. Filters are employed to filter out any unwanted frequencies, generally called noise, due to the nonlinear characteristics of some electronic devices or signals picked up from the surrounding medium.

The experiment is to design the filters and consequently look at the difference between the two types of filters using recorded data through practical experiments.

Background Theory

There are two types of filters in this experiment and each one consists of different components. In this segment I will be looking at each filter more directly to distinguish both the explicit differences as well as the implicit differences. Filters provide a way of taking in signals and allowing those frequencies to pass that are desired and prevent unwanted frequencies to go through.

A passive filter is a type of electronic filter that is made only from passive elements - in contrast to an active filter; it does not require an external power source (beyond the signal). Since most filters are linear, in most cases, passive filters are composed of just the four basic linear elements and they are:

  • Resistors - A device used to control current in an electric circuit by providing resistance
  • Capacitors - An electric circuit element used to store charge temporarily, consisting in general of two metallic plates separated and insulated from each other by a dielectric
  • Inductors - One that inducts, especially a device that functions by or introduces inductance into a circuit
  • Transformers - A device used to transfer electric energy from one circuit to another, especially a pair of multiply wound, inductively coupled wire coils that effect such a transfer with a change in voltage, current, phase, or other electric characteristic

The second part of the experiment consisted of designing an active filter. An active filter is one which consists of all similar elements which exists in a passive filter but it also has an operational amplifier which is used to provide gain. An active filter is also based on the principle of the resistor-capacitor [RC] design, but employs an op amp in the design.  The op amp is useful, as it can supply gain. This means the input can be amplified by a set amount to provide the output. Any component that can produce gain is classed as active. Therefore, in general, there are two classifications of filters:

Join now!
  • Passive filter
  • Active filter

Resistors and capacitors were used in the buildup of the filter to manipulate the current flow. From ohms law, one of widely used equation in electronics, were V=IR, its voltage equal to current multiplied by resistance.  The current in the equation could either be direct or alternating current where both types can have any frequencies above 0 Hz.

The level of impedance (R) of a capacitor is reliant on the frequency of current (I) through it.

Impedance = 1/ jωC → C is the capacitance which is expressed in Farads

But ...

This is a preview of the whole essay