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There are many thousands of different types of diode, bipolar transistor and FET. These semiconductor devices have different characteristics according to the way they are designed and made. As a result it is essential that the different semiconductor devices are given different part numbers to distinguish them from each other. Diodes & Rectifiers at Parts Express. General-purpose rectifier diode, logic diode, small-signal fast switching diode, fast recovery rectifier diode in-stock. Open Accessibility menu Press the enter key to adjust the page for a screen reader. The second letter is ‘N’, and then the first digit is 1 for diodes, 2 for transistors, 3 for four-leaded devices, and so forth. But 4N and 5N are only used for optocouplers. The sequential numbers run from 100 to 9999 and indicate the approximate time the device was first made.
What is a Tunnel Diode?
A Tunnel Diode is a heavily doped p-n junction diode. The tunnel diode shows negative resistance. When voltage value increases, current flow decreases. Tunnel diode works based on Tunnel Effect.
The following image shows the symbol of a Tunnel Diode.
Leo Esaki invented Tunnel diode in August 1957. Dlink driver download. Therefore, it is also called as Esaki diode. The materials used for this diode are Germanium, Gallium arsenide and other silicon materials. Tunnel diode shows a negative resistance in their operating range. So, it can be used as amplifier, oscillators and in any switching circuits.
Width of the Depletion Region in Tunnel Diode
When mobile charge carriers both free electrons and holes are missing, the region in a p-n junction has a region called Depletion region. To stop the flow of electrons from the n-type semiconductor and holes from the p-type semiconductor, depletion region acts as a barrier.
Depending on the number of impurities added, width of depletion region varies. To increase electrical conductivity of the p-type and n-type semiconductor impurities are added. A wide and big depletion region is formed when a smaller number of impurities is added to p-n junction diode. At the same time, when a greater number of impurities is added, narrow depletion region occurs.
The p-type and n-type semiconductor is heavily doped in a tunnel diode due to a greater number of impurities. Heavy doping results in a narrow depletion region. When compared to a normal p-n junction diode, tunnel diode has a narrow depletion width. Therefore, when small amount of voltage is applied, it produces enough electric current in the tunnel diode.
Tunneling Effect
In electronics, Tunneling is known as a direct flow of electrons across the small depletion region from n-side conduction band into the p-side valence band. In a p-n junction diode, both positive and negative ions form the depletion region. Due to these ions, in-built electric potential or electric field is present in the depletion region. This electric field gives an electric force to the opposite direction of externally applied voltage.
As the width of the depletion layer reduces, charge carriers can easily cross the junction. Charge carriers do not need any form of kinetic energy to move across the junction. Instead, carriers punch through junction. This effect is called Tunneling and hence the diode is called Tunnel Diode.
Due to Tunneling, when the value of forward voltage is low value of forward current generated will be high. It can operate in forward biased as well as in reverse biased. Due to high doping, it can operate in reverse biased. Due to the reduction in barrier potential, the value of reverse breakdown voltage also reduces. It reaches a value of zero. Due to this small reverse voltage leads to diode breakdown. Hence, this creates negative resistance region.
Tunnel Diode Working Phenomenon
Unbiased Tunnel Diode
In an unbiased tunnel diode, no voltage will be applied to the tunnel diode. Here, due to heavy doping conduction band of n – type semiconductor overlaps with valence band of p – type material. Electrons from n side and holes from p side overlap with each other and they will be at same energy level.
Some electrons tunnel from the conduction band of n-region to the valence band of p-region when temperature increases. Similarly, holes will move from valence band of p-region to the conduction band of n-region. Finally, the net current will be zero since equal numbers of electrons are holes flow in opposite direction.
P α e (-A *E *b *W)
P – Probability that the particle crosses the barrier
W – Width of the barrier
E – Energy of the barrier
Small Voltage Applied to the Tunnel Diode
When a small voltage, that has lesser value than the built-in voltage of the depletion layer, is applied to the tunnel diode, there is no flow of forward current through the junction. Nevertheless, a minimal number of electrons from the conduction band of n region will start tunneling to valence band in p region.
Therefore, this movement creates a small forward biased tunnel current. When a small voltage is applied, tunnel current starts to flow.
Increased Voltage Applied to the Tunnel Diode
When the amount of voltage applied is increased, the number of free electrons generated at n side and holes at p side is also increased. Due to voltage increase, overlapping between the bands are also increased.
Maximum tunnel current flows when the energy level of n-side conduction band and the energy level of a p-side valence band becomes equal.
Further Increased Voltage Applied to the Tunnel Diode
A further increase in the applied voltage will cause a slight misalignment of the conduction band and valence band. Still there will be an overlap between conduction band and valence band. The electrons move from conduction band to valence band of p region. Therefore, this causes small current to flow. Hence, tunnel current starts decreasing.
Largely Increased Voltage Applied to the Tunnel Diode
The tunneling current will be zero when applied voltage is increased more to the maximum. At this voltage levels, the valence band and the conduction band does not overlap. This makes tunnel diode to operate same as a PN junction diode.
When applied voltage is more than the built-in potential of the depletion layer the forward current starts flowing through the tunnel diode. In this condition, current portion in the curve decreases when the voltage increases and this is the negative resistance of tunnel diode. Such diodes operating in negative resistance region is used as amplifier or oscillator.
V-I Characteristics of Tunnel Diode
Due to forward biasing, because of heavy doping conduction happens in the diode. The maximum current that a diode reaches is Ip and voltage applied is Vp. The current value decreases, when more amount of voltage is applied. Current keeps decreasing until it reaches a minimal value.
The small minimal value of current is Iv. From the above graph, it is seen that from point A to B current reduces when voltage increases. That is the negative resistance region of diode. In this region, tunnel diode produces power instead of absorbing it.
Applications of Tunnel Diode
- Tunnel diode can be used as a switch, amplifier, and oscillator.
- Since it shows a fast response, it is used as high frequency component.
- Tunnel diode acts as logic memory storage device.
- They are used in oscillator circuits, and in FM receivers. Since it is a low current device, it is not used more.
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There are many thousands of different types of diode, bipolar transistor and FET. These semiconductor devices have different characteristics according to the way they are designed and made.
As a result it is essential that the different semiconductor devices are given different part numbers to distinguish them from each other.
Initially manufacturers had to give their own numbers to devices, but soon standard part numbering schemes were used for semiconductor devices including diodes, bipolar transistors and FETs - both JFETs and MOSFETs.
Having industry standard numbering schemes for semiconductor devices has many advantages, not only for large scale manufacturers of electronic equipment right down to the hobbyist and student.
Semiconductor device numbering / coding schemes
There are many different ways of organising a numbering scheme. In the early days of thermionic valve (vacuum tube) manufacture, each manufacturer gave a number to the types they manufactured. In this way there were vast numbers of different numbers for devices many of which were virtually identical. It soon became obvious that a more structured approach was required, so that the same device could be bought regardless of the manufacturer.
The same is true for semiconductor devices, and manufacturer independent numbering schemes are used for diodes, bipolar transistors and FETs. In fact there a few semiconductor numbering schemes in use:
- Pro-electron numbering scheme This diode, bipolar transistor and FET numbering scheme was originated in Europe and is widely used for transistors developed and manufactured here.
- JEDEC numbering scheme This diode and transistor numbering scheme was originated in the USA and it is widely used for diodes and transistors that originate from North America.
- JIS numbering scheme This semiconductor device numbering system was developed in Japan and can be seen on diodes, transistors and FETs that are made in Japan.
- Manufacturers own schemes: There are some devices, particularly specialised bipolar transistors and some FETs for which individual manufacturers may wish to retain all the manufacturing rights. They may not want to open up the specifications and manufacturing methods to others is they are using a technique they have developed. In these and similar instances, manufacturers will use their own part numbering schemes that do not conform to the industry standard schemes
The aim of the the industry standard numbering schemes is to allow for the identification and description of electronic components and in this case semiconductor devices including diodes, bipolar transistors and field effect transistors, to have common electronic components and component numbering across several manufacturers. To achieve this, manufacturers register a definition for new electronic components with the relevant agency and then receive a new part number.
This approach enables electronic equipment manufacturing companies to have second sources for their components and in this way assure the supply for large scale manufacturing and also to reduce the effects of obsolescence.
To varying degrees these numbering schemes allow for a broad description of the function of the diode, transistor or FET. The Pro-Electron scheme providing far more information than the others.
Pro-Electron or EECA Numbering Coding System
The Pro-Electron numbering scheme to provide a standardised scheme for semiconductor numbering - in particular diodes, transistors and fild effect transistors was set up in 1966 at a meeting in Brussels, Belgium.
The scheme for the numbering of semiconductor diodes, bipolar transistors and FETs was based around the format of the system developed by Mullard and Philips for thermionic valve or vacuum tube numbering that had existed since the early 1930s. In this the first letter designated the heater voltage and current, the second and subsequent letters the individual functions within the glass envelope and the remaining numbers indicated the valve based and the serial number for the type.
The Pro-Electron scheme took this and used letters that were seldom used for the heater descriptions to designate the semiconductor type and then used the second letter to define the function. Similarities existed between the valve / tube designations and those used for the semiconductor devices. For example, 'A' was used for a diode, etc.
The scheme was widely used and in 1983 its management was taken over by the European Electronic Component Manufacturers Association, EECA.
First letter
- C = Gallium Arsenide
- R = Compound materials
Second letter
- A = Diode - low power or signal
- B = Diode - variable capacitance
- C = Transistor - audio frequency, low power
- D = Transistor - audio frequency, power
- E = Tunnel diode
- F = Transistor - high frequency, low power
- G = Miscellaneous devices
- H = Diode - sensitive to magnetism
- L = Transistor - high frequency, power
- N = Photocoupler
- P = Light detector
- Q = Light emitter
- R = Switching device, low power, e.g. thyristor, diac, unijunction
- S = Transistor - switching low power
- T = Switching device, low power, e.g. thyristor, triac
- U = Transistor - switching, power
- W = Surface acoustic wave device
- X = Diode multiplier
- Y = Diode rectifying
- Z = Diode - voltage reference
Subsequent characters
The characters following the first two letters form the serial number of the device. Those intended for domestic use have three numbers, but those intended for commercial or industrial use have letter followed by two numbers, i.e. A10 - Z99.
Suffix
On some occasions there may be a suffix letter that is added:
- C = high gain
- No suffix = gain unclassified
This is useful to both manufacturers and users because when transistors are manufactured, there is a large spread in the levels of gain. They can then be sorted into groups and marked according to their gain.
Using the numbering scheme it can be seen that a transistor with the part number BC107 is a silicon low power audio transistor and a BBY10 is silicon variable capacitance diode for industrial or commercial use. A BC109C for example is a silicon low power audio transistor with a high gain
JEDEC Numbering or Coding System
JEDEC, Joint Electron Device Engineering Council is an independent industry semiconductor engineering trade organisation and standardisation body. It provides many functions, one of which is the standardisation of semiconductor, and in this case, diode, bipolar transistor and field effect transistor part numbering.
The earliest origins of JEDEC can be traced back to 1924 when the Radio Manufacturers Association was established - many years later this became the Electronic Industries Association, EIA. In 1944, the Radio Manufacturers Association and the National Electronic Manufacturers Association established a body called the Joint Electron Tube Engineering Council, JETEC. This was set up with the aim of assigning and coordinating type numbers of electron tubes, (thermionic valves).
With the increasing use of semiconductor devices, the scope of JETEC was broadened and it was renamed JEDEC, Joint Electron Device Engineering Council in 1958.
Initial numbering of the semiconductor devices followed the broad outlines of the tube of valve numbering scheme that had been developed: '1' stood for 'No filament / heater' and the 'N' stood for 'crystal rectifier'.
Download dynojet research driver. The first digit for semiconductor device numbering was repurposed from indicating no filament to the number of PN junctions in the semiconductor device, and the numbering system was described in EIA/JEDEC EIA-370.
- First Number =
- 1 = Diode
- 2 = Bipolar transistor or single gate field effect transistor
- 3 = Dual gate field effect transistor
- Second Letter = N
- Subsequent numerals = Serial number
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Thus a device with the numbering code 1N4148 is a diode and a 2N706 is a bipolar transistor.
Sometimes extra letters are added to the part number and these often refer to refer to the manufacturer. M means the manufacturer is Motorola, while TI means Texas Instruments, although an A added to the part number often means a revision of the specification, e.g. 2N2222A transistors are widely available and these are an updated version of the 2N2222. Interpreting these numbers sometimes requires a little background knowledge.
JIS semiconductor device numbering scheme
The Japanese Industrial Standards, JIS part numbering scheme for semiconductor devices is standardised under JIS-C-7012.
This scheme uses a type number that comprises of a number followed by two characters and then this is followed by a serial number.
First Number Drivers etr.
The first number indicates the number of junctions int he semiconductor device.
- 1 = Diode
- 2 = Bipolar transistor or single gate field effect transistor
- 3 = Dual gate field effect transistor
Letters in positions 2 & 3
- SA = PNP high frequency bipolar transistor
- SB = PNP audio frequency bipolar transistor
- SC = NPN high frequency bipolar transistor
- SD = NPN audio frequency bipolar transistor
- SE = Diodes
- SF = Thyristor (SCR)
- SG = Gunn devices
- SH = UJT (Unijunction transistor)
- SJ = P-channel JFET / MOSFET
- SK = N-channel JFET / MOSFET
- SM = Triac
- SQ = LED
- SR = Rectifier
- SS = Signal diode
- ST = Avalanche diode
- SV = Varactor diode / varicop diode
- SZ = Zener diode / voltage reference diode
Serial number
The serial number follows the first digit and the two semiconductor device type letters. The numbers run between 10 and 9999.
Suffix
Following the serial number a suffix can be used to indicate the device has been type approved, i.e. there is a guarantee that it has been manufactured under the right conditions to produce the required semiconductor device.
Manufacturer numbers
Despite the fact that there are industry organisations in place to generate device numbers, some manufacturers wanted to produce devices that were unique to them. In some areas it would provide a device with a unique selling point that other manufacturers could not copy.
These semiconductor devices numbers are unique to the manufacturer and as a result they can be used to identify the source.
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Some common examples are given below:
- MJ = Motorola power, metal case
- MJE = Motorola power, plastic case
- MPS = Motorola low power, plastic case
- MRF = Motorola RF transistor
- TIP = Texas Instruments power transistor (plastic case)
- TIPL = TI planar power transistor
- TIS = TI small signal transistor (plastic case)
- ZT = Ferranti
- ZTX = Ferranti
The Pro-electron transistor and diode numbering or coding system provides more information about the device, than the JEDEC system. However both of these diode and transistor numbering schemes are widely used and enable the same device types to be made by a number of manufacturers. This enables equipment manufacturers to buy their semiconductors from a number of different manufactures and know that they are buying devices with the same characteristics.
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