Reverse leakage current in transistor

Reverse leakage current in transistor

In electronicsleakage is the gradual transfer of electrical energy across a boundary normally viewed as insulating, such as the spontaneous discharge of a charged capacitormagnetic coupling of a transformer with other components, or flow of current across a transistor in the "off" state or a reverse-polarized diode. Gradual loss of energy from a charged capacitor is primarily caused by electronic devices attached to the capacitors, such as transistors or diodes, which conduct a small amount of current even when they are turned off.

Even though this off current is an order of magnitude less than the current through the device when it is on, the current still slowly discharges the capacitor. Another contributor to leakage from a capacitor is from the undesired imperfection of some dielectric materials used in capacitors, also known as dielectric leakage. It is a result of the dielectric material not being a perfect insulator and having some non-zero conductivity, allowing a leakage current to flow, slowly discharging the capacitor.

Another type of leakage occurs when current leaks out of the intended circuit, instead flowing through some alternate path.

Reverse body biasing of a transistor using a photovoltaic source

This sort of leakage is undesirable because the current flowing through the alternate path can cause damage, fires, RF noise, or electrocution. Leakage in a high- voltage system can be fatal to a human in contact with the leak, as when a person accidentally grounds a high-voltage power line. Leakage may also mean an unwanted transfer of energy from one circuit to another.

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For example, magnetic lines of flux will not be entirely confined within the core of a power transformer ; another circuit may couple to the transformer and receive some leaked energy at the frequency of the electric mains, which will cause audible hum in an audio application.

Leakage current is also any current that flows when the ideal current is zero. Such is the case in electronic assemblies when they are in standby, disabled, or "sleep" mode standby power. These devices can draw one or two microamperes while in their quiescent state compared to hundreds or thousands of milliamperes while in full operation. These leakage currents are becoming a significant factor to portable device manufacturers because of their undesirable effect on battery run time for the consumer.

In semiconductor devicesleakage is a quantum phenomenon where mobile charge carriers electrons or holes tunnel through an insulating region. Leakage increases exponentially as the thickness of the insulating region decreases. Tunneling leakage can also occur across semiconductor junctions between heavily doped P-type and N-type semiconductors.

Other than tunneling via the gate insulator or junctions, carriers can also leak between source and drain terminals of a Metal Oxide Semiconductor MOS transistor. This is called subthreshold conduction. The primary source of leakage occurs inside transistorsbut electrons can also leak between interconnects.

Leakage increases power consumption and if sufficiently large can cause complete circuit failure. Leakage is currently one of the main factors limiting increased computer processor performance. Leakage reduction to continue Moore's law will not only require new material solutions but also proper system design. Certain types of semiconductor manufacturing defects exhibit themselves as increased leakage. Thus measuring leakage, or Iddq testingis a quick, inexpensive method for finding defective chips.

Increased leakage is a common failure mode resulting from non-catastrophic overstress of a semiconductor device, when the junction or the gate oxide suffers permanent damage not sufficient to cause a catastrophic failure.

Solved Problems on Transistor

Overstressing the gate oxide can lead to stress-induced leakage current. In bipolar junction transistorsthe emitter current is the sum of the collector and base currents. The collector current has two components: minority carriers and majority carriers. The minority current is called the leakage current [ clarification needed ]. In hetrostructure field-effect transistors HFETs the gate leakage is usually attributed to the high density of traps residing within the barrier.

Leakage current is generally measured in microamperes. For a reverse-biased diode it is temperature sensitive. Leakage current must be carefully examined for applications that work in wide temperature ranges in order to know the diode characteristics.

From Wikipedia, the free encyclopedia. Categories : Electrical parameters Electric current. Hidden categories: Webarchive template wayback links Wikipedia articles needing clarification from November Welcome, Guest. Please login or register. Did you miss your activation email? This topic This board Entire forum Google Bing. Print Search. Author Topic: Reverse leakage current of zener Posts: Country:.

Do you know which one is correct? One is a 5V1 zener, and the other an 8V2 zener. The larger value of leakage current is a maximum specification. It is a practical value to measure quickly on automated testing equipment in production. The smaller value is a typical or characteristic value, based on careful measurements with laboratory equipment over a range of temperature values, and is not guaranteed from individual part to individual part.

reverse leakage current in transistor

This difference between guaranteed performance and typical performance is typical of these datasheets, and not suspicious. The following users thanked this post: opampsmoker. If leakage current is critical for some reason you will have to measure and bin your own under the appropriate test conditions. Keep in mind that temperature will have a huge effect. What is the 'back-to-back zener effect" you are looking for?

The circuit you posted makes little sense to me--what is the story? Quote from: opampsmoker on November 20,pm. Modification for Low leakage current zeners. PNG The following users thanked this post: wraperopampsmoker.

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I think when leakages are in series, the overall leakage seen is the level of the lowest leakage current? Quote from: opampsmoker on November 21,am. Quote from: opampsmoker on November 21,pm. There was an error while thanking.

reverse leakage current in transistor

SMF 2. EEVblog on Youtube.An important conduction limitation of PN junction diode is leakage current. When a diode is reverse biased, the width of the depletion region increases. Generally, this condition is required to restrict the current carrier accumulation near the junction.

Majority current carriers are primarily negated in the depletion region and hence the depletion region acts as an insulator. Normally, current carriers do not pass through an insulator. It is seen that in a reverse-biased diode, some current flows through the depletion region. This current is called leakage current. Leakage current is dependent on minority current carriers.

As we know that the minority carriers are electrons in the P type material and holes in the N type material. Minority carriers of each material are pushed through the depletion zone to the junction. This action causes a very small leakage current to occur. Generally, leakage current is so small that it can be considered as negligible. Here, in case of leakage current, temperature plays an important role. The minority current carriers are mostly temperature dependent.

When the surrounding temperature rises, it causes significant increase in minority carrier creation and as a result it causes a corresponding increase in leakage current.

In all reverse-biased diodes, occurrence of leakage current is normal to some extent. In Germanium and Silicon diodes, leakage current is only of few microamperes and nanoamperesrespectively.

Germanium is much more susceptible to temperature than silicon. For this reason, mostly Silicon is used in modern semiconductor devices. Semiconductor Devices - Leakage Current Advertisements.

Previous Page. Next Page. Previous Page Print Page. Dashboard Logout.A metal oxide semiconductor MOS transistor has a source terminal, a drain terminal, a gate terminal and a body terminal. The source terminal is connected to receive a supply voltage and the body terminal is connected to receive a reverse body bias voltage.

A photovoltaic circuit has a first terminal connected to the source terminal of the MOS transistor and a second terminal connected to the body terminal of the MOS transistor.

The photovoltaic circuit converts received photons from the environment to generate the reverse body bias voltage. The present invention relates to body biasing of transistors in a digital circuit and, in particular, to the implementation of a reverse body biasing of a digital circuit transistor where the reverse body bias voltage is generated using an energy harvesting source such as a photovoltaic circuit.

It is well known in the art to apply a body bias to the well body region of a metal oxide semiconductor field effect transistor MOSFET in order to influence the properties of the transistor channel. For example, a forward body bias FBB applied to the well influences device operation by decreasing the threshold voltage Vt of the transistor.

This results in a faster operating device due to increase in the channel current at the expense of increased leakage current. Conversely, a reverse body bias RBB applied to the well influences device operation by increasing the threshold voltage Vt of the transistor.

This results in a device which exhibits a lower leakage current at the expense of a reduced speed. It is accordingly clear that circuit designers can use body bias selection to modulate transistor threshold voltage in effectuating a tradeoff between power and speed for the circuit operation. There is an increased interest in circuits which operate at ultra-low voltage levels. For example, voltage levels equal to or less than 0.

It is common for that digital circuitry to operate in a suspended operating mode such as sleep or deep-sleepand when in this mode it is important that the transistors of the digital circuitry have a reduced leakage current. To address this concern, the circuit designer may choose to use a reverse body bias RBB applied to the transistor well body.

In these schemes, the body of a p-channel transistor pMOS is connected to a voltage source producing a voltage for example, Vdds that is larger i. As shown in FIG. The n-well bias generator circuit 16 is typically a positive charge pump circuit and the p-well bias generator circuit 18 is typically a negative charge pump circuit.

A problem with this implementation is that the charge pump circuits for the bias generator circuits 16 and 18 consume some amount of power overhead from the supply voltage Vdd. There is a need in the art to address the noted drawbacks of prior art reverse body biasing schemes. In an embodiment, a circuit comprises: a metal oxide semiconductor MOS transistor having a source terminal, a drain terminal, a gate terminal and a body terminal; wherein the source terminal is connected to receive a supply voltage; and a photovoltaic circuit having a first terminal connected to the source terminal of the MOS transistor and a second terminal connected to the body terminal of the MOS transistor, wherein the photovoltaic circuit converts received photons to generate a reverse body bias voltage applied to the body terminal of the MOS transistor.

In an embodiment, a circuit comprises: a metal oxide semiconductor MOS transistor having a source terminal, a drain terminal, a gate terminal and a body terminal; wherein the source terminal is connected to receive a supply voltage; and an energy harvesting circuit having a first terminal connected to the source terminal of the MOS transistor and a second terminal connected to the body terminal of the MOS transistor, wherein the energy harvesting circuit harvests energy to generate a reverse body bias voltage applied to the body terminal of the MOS transistor.

For a better understanding of the embodiments, reference will now be made by way of example only to the accompanying figures in which:. Reference is now made to FIG. The digital circuit is powered by a power supply circuit 20 that is configured to provide a power supply domain with a positive supply voltage Vdd and a ground voltage Gnd. In an ultra-low voltage circuit application, Vdd may be equal to a voltage of 0. The digital circuit is represented here in a simplified form by just a single CMOS digital logic inverter gate 10 comprising a pMOS transistor 12 and an nMOS transistor 14 coupled in series with each other.

The source terminal of the pMOS transistor 12 is coupled to a supply node 22 receiving the positive supply voltage Vdd.

The source terminal of the nMOS transistor 14 is coupled to a supply node 24 receiving the ground supply voltage Gnd. The diode for the photovoltaic cell PVpos has a cathode coupled to the supply node 22 receiving the positive supply voltage Vdd and an anode coupled to a more positive supply node 32 at which the reverse body bias voltage Vdds is generated.

This reverse body bias voltage Vdds is applied to the well s of the pMOS transistor s The diode for the photovoltaic cell PVneg has an anode coupled to the supply node 24 receiving the ground supply voltage Gnd and a cathode coupled to a more negative supply node 34 at which the reverse body bias voltage Gnds is generated. This reverse body bias voltage Gnds is applied to the well s of the nMOS transistor s The integrated circuit device 40 includes digital logic circuitry 42 powered by a power supply domain with a positive supply voltage Vdd and a ground voltage Gnd.

The pMOS transistors 44 each include a source terminal, a drain terminal, a gate terminal and a body well terminal. The nMOS transistors 46 each include a source terminal, a drain terminal, a gate terminal and a body well terminal. The integrated circuit device 70 includes digital logic circuitry 42 and an imaging circuit 80 that are powered by a power supply domain with a positive supply voltage Vdd and a ground voltage Gnd.

The imaging circuit 80 includes an array 82 of photodetectors such as photodiodes for receiving photons A sense and convert circuit 84 senses the signals generated by the photodetectors in the array 82 and performs a conversion to generate digital image signals 86 for processing by the digital logic circuitry Reverse leakage current in a semiconductor device is the current from that semiconductor device when the device is reverse biased.

When a semiconductor device is reverse biased it should not conduct any currenthowever, due to an increased barrier potential, the free electrons on the p side are dragged to the battery's positive terminal, while holes on the n side are dragged to the battery's negative terminal.

This produces a current of minority charge carriers and hence its magnitude is extremely small. For constant temperatures, the reverse current is almost constant although the applied reverse voltage is increased up to a certain limit. Hence, it is also called reverse saturation current. The term is particularly applicable to mostly semiconductor junctions, especially diodes and thyristors. The leakage current increased with temperature.

As an example, the Fairchild Semiconductor FDVN has a reverse leakage of up to 1 microamp at room temperature rising to 10 microamps with a junction temperature of 50 degrees Celsius. For all basic purposes, leakage currents are very small, and, thus, are normally negligible. From Wikipedia, the free encyclopedia. This article does not cite any sources. Please help improve this article by adding citations to reliable sources.

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Deutsch Edit links. This electronics-related article is a stub. You can help Wikipedia by expanding it.Here the output resistance is very high as compared to input resistance, since the input junction base to emitter of the transistor is forward biased while the output junction base to collector is reverse biased.

BJT Second Order Effects: Reverse Leakage Current

When the emitter circuit is open as shown in Fig. The leakage current ICBO is the current that flows through the base-collector junction when emitter is open as shown is Fig.

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When the transistor is in CE arrangement, the base current i. For this transistor, if the base current is allowed to exceed 1. Fig 11 shows the open circuit failures in a transistor. We shall discuss the circuit behaviour in each case. Since the collector diode is not forward biased, it is OFF and there can be neither collector current nor base current.

Therefore, there will be no voltage drops across either resistor and the voltage at the base and at the collector leads of the transistor will be 12V. Since the base is open, there can be no base current so that the transistor is in cut-off.

Therefore, all the transistor currents are 0A. In this case, the base and collector voltages will both be at 12V. In this case, the emitter diode is still ON, so we expect to see 0. However, we will see 12V at the collector because there is no collector current. This locates the point A of the load line on the collector current axis.

By joining these two points, we get the d. This locates the point B of the load line. This locates the point A of the load line. By joining these two points, load line AB is constructed as shown in Referring to Fig.

This locates the point B of the load line on the collector-emitter voltage axis as shown in Fig. The transistor circuit shown in Fig.

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By joining points A and B, d. As we decrease R Bbase current and hence collector current increases. The increased collector current causes a greater voltage drop across R C ; this decreases the collector-emitter voltage. At this point, collector-base junction is no longer reverse biased and transistor action is lost.

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Semiconductor Devices - Leakage Current

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