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Why is the control grid of a triode maintained at a negative potential?
Wiki User
∙ 15y ago
The voltage on the control grid in a triode controls the current flowing from the cathode to the anode. When the grid goes negative, the tube is said to be cut off and no current will flow. When it goes positive, current starts to flow. As it goes more positive, more current flows. At some point, increasing the grid voltage won't cause any more cathode-to-anode current (plate current), and we call that saturation. We have to decide what to set the grid voltage at, and that is what we call biasing the tube. (We need to bias it.) Where do we want the tube operating with no signal applied? What kind of circuit is it in and how are we going to operate it? Class A, class B, class C or class AB? If a triode is set up with the grid negative all the time, no plate current will flow. If we set it up so that the grid is negative a little bit, then the input signal will have to go positive enough to overcome this voltage before plate current will flow. During the negative portion of the input signal, the tube will be cut off. Remember that it will only have plate current for a portion of the positive half of the input signal when the input voltage exceeds the "set" voltage on the grid (the bias voltage). This means that the amplifier will be operating class C. The class C amplifier operates for less than 180 degrees of the input signal.
Wiki User
∙ 15y ago
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What is a crystal triode?
A crystal triode is the old term for transistor. Crystal diodes were well established by the time transistors were invented, so using vacuum tube terminology, the logical name for a diode whose current could be controlled by a third element was "crystal triode".
What is a TRIODE and what are its uses?
A triode is a vacuum-tube (US) aka valve(UK) with three electrodes : an anode, a cathode and a grid. The cathode is heated electrically which boils off a cloud of electrons. The anode is made positive ( typ. 100-500V) which attracts the electrons towards it. The grid is an open structure, usually of thin wires, placed between the anode and cathode, but nearer the cathode. If a negative voltage is applied to the grid the current flow through the tube is reduced. The more negative, the less current. Prior to the development of transistors, tubes were used for all things in radio,TV and electronics. Different tubes had different numbers of electrodes; the triode was particularly suited to high power amplifiers, especially at radio frequencies. Triodes are still used today by shortwave radio stations, and for RF heating equipment.
What is the full form of TRIAC?
TRIAC is the word derrived from the 2 words TRIode and AC.
What are the advantages of using transistor as an switch instead of diode?
1. A transistor *is* a triode- this is the general name for any three-electrode electronic device. 2. Most people understand "triode" to mean a tride vacuum tube/valve. 3. The transistor (i) needs no heated filament/cathode, so it uses much less power than a valve triode, (ii) because of (i), transistors do not "burn out" with age, so they have much longer lifetimes, are much more reliable, and generate much less waste heat, (iii) transistors can operate at much lower power than triode valves, and at much higher frequencies, (iv) transistors can be made much smaller than triodes, by a factor of many tens of thousands, (v) from early on, transistors were much cheaper than triode valves.
What is vaccume tube?
A vacuum tube is an instrument used to control the flow of electrons. The simplest form of this is called the triode and has three elements. An anode, a cathode, and a grid. The flow of electrons is always from anode to cathode the grid can influence the flow of the electrons. Like the light bulb the tube needs to be a vacuum or filled with gas to prevent the metals they are made of from catching on fire and melting. The first person to discover that a grid could have an electric charge was Lee De Forest. See also: Lee De Forest Edwin Armstrong David Sarnoff
The grid in a high-vacuum triode is usually kept?
negative
What is an equivalent diode of a triode valve?
Hard to answer this one.The triode is a diode with a control electrode (the grid) added.The only useful answer is that a triode is a voltage-controlled doide.Try asking the question so that it can be answered more usefully.
What is the advantage of triode?
With a diode tube you have no control over the current flow and it can only be used as a rectifier, where the triode consist of a control grid, to control the flow of electrons that will reach the anode, this make it possible to use the triode as a amplifier, compared to a transistor the control grid have the same function as the base of the transistor.Advantages?Over tetrodes and pentodes:1. Operation at higher radio frequencies,2. Lower noise figures,3. Simpler circuitry and only one power supply.
A grid in a high vacuum diode is usually kept negatively charged with respect to the cathode so that the electrons may be?
the grid is negative so it can control the amount of electrons coming off the cathode. To stop or decrease intensity of cathode ray/electron beam, it is made more negative (to repel electrons as negative charge and negative charge repel) and to increase intensity, the grid is made less negative.
Was the first amplifying tube a triode?
If by triode, you mean "a three-electrode tube", then yes. You need a source of current into the device, a control electrode, and an "outlet" for the controlled current. Although there were radically different types of construction, all early amplifying tubes were triodes of some kind.
Why you use tetrode instead of triode?
a tetrode is used when you need a screen grid tube, but a suppressor grid tube can't be used.OK, but the question was "why use a tetrode instead of a triode?"So, the answer...1. A tetrode has a higher voltage/power gain than a triode.2. A tetrode has less anode-grid feedback capacitance than a triode, and can operate in common-cathode radio frequency circuits without the neutralisation (or other corrective circuitry) that is needed by a triode.
How a triode works as basic amplifier?
A triode works as a basic amplifier by the use of radio waves. The radio waves produce a heat that is amplified.
Can be a triode tube PET 25W be damage due to electric fluctuation?
Can a triode tube PET 25W be damaged due to electric fluctuation
What is a crystal triode?
A crystal triode is the old term for transistor. Crystal diodes were well established by the time transistors were invented, so using vacuum tube terminology, the logical name for a diode whose current could be controlled by a third element was "crystal triode".
Who is the inventor of vacuum tubes?
Sir John Ambrose Fleming patented the thermionic diode in 1904. Then Lee DeForest put a control grid into it to create the triode in 1906.
Who invented the triode?
In 1906 Lee De Forest, an American engineer (often called the "father of radio"), invented the three-element vacuum tube, or triode.
What is an electronic vacuum valve with three electrodes?
Triode
