A diode is a two-terminal semiconductor device whose purpose is to conduct current in one direction only and prevent it from flowing back. Meanwhile, a rectifier is a circuit that converts alternating current AC into direct current DC. While there are many different types of amplifier, the most common are:. The difference between the two is simple : in an active setup, the system has a built-in amplifier, while in a passive one the system requires an external amplifier, which is connected by speaker wire.
Amplifiers can also be connected in series to increase the amount of power available. Usually used in professional audio systems, a bridged configuration involves two channels of a stereo amplifier being fed the same signal, while a loudspeaker the bridge is connected between those two channels to create a mono amplifier with twice the power. For paralleled setups, multiple amplifiers send the same signal to both speakers in a stereo system for increased output drive.
Well-known applications for amplifiers include stereo systems, hearing aids, wireless communications and television receivers. Amplifiers can also take the form of electromagnetic devices known as transformers, which boost voltage while keeping it constant.
Transistor as an amplifier: In an amplifier you apply a small amout of power to the transistor at all times and this closes the 'switch', allowing signal to pass through the device. Adding this positive voltage to the device is to 'bias' the device. When the weak input signal passes through it gains strength from the bias which adds to the output signal.
This is good but doesn't really make for a big amplification. Two transistors: When we put two transistors together we can have one supply a slightly amplified AC signal to the base lead of the next, thus allowing more powerful signal to flow through the second transistor and make more dramatic changes in the second transistor.
The AC wave form remains intact as the original signal, it is just stronger. So you can imagine that a large amount of water pressure is amassed in one side of a valve the collector side , it's just waiting to rush down the pipe, all you need to do is turn a knob and make slight adjustments on the base side and the the door will open part way or full way.
Water will gush through, or just trickle through. This is how we make a little bit of effort weak signal control a serious amount of power. To make an operational amplifier you use multiple transistors along with resistors and capacitors, this way you can amplify a range of frequencies. There are a ways to design these circuits but you can start with a few basic models.
Capacitor used before the transistor: transistor amplifiers use a capacitor before the input of the transistor in order to 'center' the DC signal coming from a microphone. Microphones resonate, creating negative and positive DC energy. They also use a 'bias' but for a different reason than transistors. The bias in the microphone energizes the device and puts 0 db up above 0 voltage.
The bias in most microphones requires you to supply it with about 2 volts, but it can be different. The capacitor before the transistor brings the 2 volt bias down to actual 0, and therefore removes the DC offset. The transistor needs this to work. Complications: Creating an amplifier circuit gets complicated due to things like signal noise. We recommend you start building simple amplifiers from kits in order to get the basics down.
Than after that you can tweak more powerful and expensive systems. The advent of the triode in revolutionized telephone and radio. There are many kinds of vacuum tubes used to amplify and we still use some of them today. Tube amps may use tetrodes, triodes and pentode vacuum tubes to do the job of signal amplification. The triode amplifier: This tube has a hot cathode in the center surrounded by a metal grid with the anode surrounding that.
The cathode emits electrons, and in the vacuum electrons freely flow through the grid to the anode. By energizing the grid negatively you repel more electrons, this means that less electrons can pass through the grid to get to the anode.
If you take weak audio signal a varying voltage and apply it to the grid, you'll be letting more power through the grid during positive spikes and less on negative, thus you can greatly amplify the signal. The bad part about tube amplifiers is that they consume more power and space than transistors. The hot cathode in a tube is made of a tungsten and thorium filament. This filament, just like a lightbulb will burn out after a number of hours and the tube will have to be replaced.
When you attach an amplifier to a speaker the amplifier's behavior will change. Loudspeaker impedance will change as the load changes, and this effects the entire system.
Guitarists will argue that sound from a tube amplifier is better than that from transistor-based amplifiers. Tube amp systems have non-linear clipping and more second-order harmonic distortion, there are plenty of detailed articles out there on this subject. Solid state amplifiers designed for guitarists now use current feedback circuits to increase the output impedance, this gives a similar sound from the speaker that a tube amplifier would.
We will use a simple guitar amplifier with three tubes to demonstrate how the signal is transformed from a weak 0. See the 38 minute video listed at the bottom here to go into more depth if you need. In our diagrams below we have omitted resistors and most capacitors in order to focus on the action of amplification.
In the graphic above you'll see the layout which consists of a power supply transformer connected to a rectifier tube and two other tubes. The transformer converts V from the wall into three separate lines. The 6V line just powers the filaments in the two amplifier tubes. It keeps the filaments hot so the tubes can work. The 5 V line goes to the power rectifier and warms up that tube. The Web This site. An amplifier is used to increase the amplitude of a signal waveform, without changing other parameters of the waveform such as frequency or wave shape.
They are one of the most commonly used circuits in electronics and perform a variety of functions in a great many electronic systems. The general symbol for an amplifier is shown in Fig 1. The symbol gives no detail of the type of amplifier described, but the direction of signal flow can be assumed as flowing from left to right of the diagram. Amplifiers of different types are also often described in system or block diagrams by name. For example look at the block diagram of an analogue TV receiver in Fig 1.
Also notice that the names indicate the type of amplifier used. In some cases the blocks shown are true amplifiers and in others, the amplifier has extra components to modify the basic amplifier design for a special purpose. This method of using relatively simple, individual electronic circuits as "building blocks" to create large complex circuits is common to all electronic systems; even computers and microprocessors are made up of millions of logic gates, which are simply specialised types of amplifiers.
Therefore to recognise and understand basic circuits such as amplifiers is an essential step in learning about electronics. One way to describe an amplifier is by the type of signal it is designed to amplify. This usually refers to a band of frequencies that the amplifier will handle, or in some cases, the function that they perform within an electronic system. Audio frequency amplifiers are used to amplify signals in the range of human hearing, approximately 20Hz to 20kHz, although some Hi-Fi audio amplifiers extend this range up to around kHz, whilst other audio amplifiers may restrict the high frequency limit to 15kHz or less.
Audio voltage amplifiers are used to amplify the low level signals from microphones, tape and disk pickups etc. With extra circuitry they also perform functions such as tone correction equalisation of signal levels and mixing from different inputs, they generally have high voltage gain and medium to high output resistance. Audio power amplifiers are used to receive the amplified input from a series of voltage amplifiers, and then provide sufficient power to drive loudspeakers.
Intermediate Frequency amplifiers are tuned amplifiers used in radio, TV and radar. Their purpose is to provide the majority of the voltage amplification of a radio, TV or radar signal, before the audio or video information carried by the signal is separated demodulated from the radio signal.
They operate at a frequency lower than that of the received radio signal, but higher than the audio or video signals eventually produced by the system.
The frequency at which I.
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