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{{Short description|Property that an increasing voltage results in a decreasing current}}{{Good article}}{{Use American English|date = April 2019}}File:Fluorescent light strip 2 tube.JPG|thumb|upright=1.3|Fluorescent lamp, a device with negative differential resistance.BOOK , In operation, an increase in current through the fluorescent tube causes a drop in voltage across it. If the tube were connected directly to the power line, the falling tube voltage would cause more and more current to flow, causing it to arc flash and destroy itself. To prevent this, fluorescent tubes are connected to the power line through a ballast. The ballast adds positive impedance (AC resistance) to the circuit to counteract the negative resistance of the tube, limiting the current.]]In electronics, negative resistance (NR) is a property of some electrical circuits and devices in which an increase in voltage across the device’s terminals results in a decrease in electric current through it.BOOK , This is in contrast to an ordinary resistor in which an increase of applied voltage causes a proportional increase in current due to Ohm’s law, resulting in a positive resistance.BOOK , Under certain conditions it can increase the power of an electrical signal, amplifying it.BOOK , JOURNAL , Negative resistance is an uncommon property which occurs in a few nonlinear electronic components. In a nonlinear device, two types of resistance can be defined: ‘static’ or ‘absolute resistance’, the ratio of voltage to current v / i, and differential resistance, the ratio of a change in voltage to the resulting change in current Delta v/Delta i. The term negative resistance means negative differential resistance (NDR), Delta v / Delta i < 0. In general, a negative differential resistance is a two-terminal component which can amplify,”In semiconductor physics, it is known that if a two-terminal device shows negative differential resistance it can amplify.” JOURNAL , converting DC power applied to its terminals to AC output power to amplify an AC signal applied to the same terminals.BOOK , They are used in electronic oscillators and amplifiers,BOOK , They can also have hysteresisJOURNAL , and be bistable, and so are used in switching and memory circuits.BOOK , Examples of devices with negative differential resistance are tunnel diodes, Gunn diodes, and gas discharge tubes such as neon lamps, and fluorescent lights. In addition, circuits containing amplifying devices such as transistors and op amps with positive feedback can have negative differential resistance. These are used in oscillators and active filters.Because they are nonlinear, negative resistance devices have a more complicated behavior than the positive “ohmic” resistances usually encountered in electric circuits. Unlike most positive resistances, negative resistance varies depending on the voltage or current applied to the device, and negative resistance devices can only have negative resistance over a limited portion of their voltage or current range. Therefore, there is no real “negative resistor” analogous to a positive resistor, which has a constant negative resistance over an arbitrarily wide range of current.File:Ganna diode 3A703B.jpg|thumb|A Gunn diode, a semiconductor device with negative differential resistance used in electronic oscillators to generate microwavemicrowave

Definitions

(File:DifferentialChordalResistance.svg|thumb|upright=0.8|An I–V curve, showing the difference between static resistance (inverse slope of line B) and differential resistance (inverse slope of line C) at a point (A).)The resistance between two terminals of an electrical device or circuit is determined by its current–voltage (I–V) curve (characteristic curve), giving the current i through it for any given voltage v across it.BOOK Negative resistance occurs in a few nonlinear (nonohmic) devices.WEB , In a nonlinear component the I–V curve is not a straight line,BOOK , so it does not obey Ohm’s law. Resistance can still be defined, but the resistance is not constant; it varies with the voltage or current through the device.BOOK , This source uses the term “absolute negative differential resistance” to refer to active resistance The resistance of such a nonlinear device can be defined in two ways,WEB , BOOK, Electromagnetic Compatibility Handbook, Kaiser, Kenneth L., CRC Press, 2004, 978-0-8493-2087-3, 13–52,books.google.com/books?id=nZzOAsroBIEC&q=%22Static+resistance%22+%22dynamic+resistance&pg=SA13-PA52, which are equal for ohmic resistances:WEB , , pp. 18–19,(File:Quadrants of IV plane.svg|thumb|The quadrants of the I–V plane,WEB, Traylor, Roger L., Calculating Power Dissipation, Lecture Notes – ECE112:Circuit Theory, Dept. of Elect. and Computer Eng., Oregon State Univ., 2008,web.engr.oregonstate.edu/~traylor/ece112/lectures/calc_power_diss.pdf, 23 October 2012, live,web.engr.oregonstate.edu/~traylor/ece112/lectures/calc_power_diss.pdf," title="web.archive.org/web/20060906041611web.engr.oregonstate.edu/~traylor/ece112/lectures/calc_power_diss.pdf,">web.archive.org/web/20060906041611web.engr.oregonstate.edu/~traylor/ece112/lectures/calc_power_diss.pdf, 6 September 2006, , inst.eecs.berkeley.edu/~ee100/fa08/lectures/EE100supplementary_notes_3.pdf" title="web.archive.org/web/20150726145426inst.eecs.berkeley.edu/~ee100/fa08/lectures/EE100supplementary_notes_3.pdf">archived showing regions representing passive devices (white) and active devices (red))

• Static resistance (also called chordal resistance, absolute resistance or just resistance) – This is the common definition of resistance; the voltage divided by the current: R_mathrm{static} = frac{v}{i} . It is the inverse slope of the line (chord) from the origin through the point on the I–V curve. In a power source, like a battery or electric generator, positive current flows out of the positive voltage terminal, opposite to the direction of current in a resistor, so from the passive sign convention i and v have opposite signs, representing points lying in the 2nd or 4th quadrant of the I–V plane (diagram right). Thus power sources formally have negative static resistance (R_text{static} < 0).BOOK

, BOOK , , see footnote p. 116 Static resistance determines the power dissipation in a component. Passive devices, which consume electric power, have positive static resistance; while active devices, which produce electric power, do not.BOOK

• Differential resistance (also called dynamic, or incremental resistance) – This is the derivative of the voltage with respect to the current; the ratio of a small change in voltage to the corresponding change in current, the inverse slope of the I–V curve at a point: r_mathrm{diff} = frac {dv}{di} . Differential resistance is only relevant to time-varying currents. Points on the curve where the slope is negative (declining to the right), meaning an increase in voltage causes a decrease in current, have negative differential resistance {{nowrap|(r_text{diff} < 0)}}. Devices of this type can amplify signals, and are what is usually meant by the term “negative resistance”.

Negative resistance, like positive resistance, is measured in ohms.Conductance is the reciprocal of resistance.BOOK , BOOK , It is measured in siemens (formerly mho) which is the conductance of a resistor with a resistance of one ohm. Each type of resistance defined above has a corresponding conductance

• Static conductance G_mathrm{static} = frac{1}{R_mathrm{static}} = frac{i}{v}
• Differential conductance g_mathrm{diff} = frac{1}{r_mathrm{diff}} = frac{di}{dv}

It can be seen that the conductance has the same sign as its corresponding resistance: a negative resistance will have a negative conductanceSome microwave texts use this term in a more specialized sense: a voltage controlled negative resistance device (VCNR) such as a tunnel diode is called a “negative conductance” while a current controlled negative resistance device (CCNR) such as an IMPATT diode is called a “negative resistance”. See the Stability conditions section while a positive resistance will have a positive conductance.{{multiple image| align = center| direction = horizontal| header =| image1 = Ohmic resistance.svg| caption1 = Fig. 1: I–V curve of linear or “ohmic” resistance, the common type of resistance encountered in electrical circuits. The current is proportional to the voltage, so both the static and differential resistance is positiveR_text{static} = r_text{diff} = {v over i} > 0 | width1 = 190| image2 = Negative differential resistance definition.svg| caption2 = Fig. 2: I–V curve with negative differential resistance (red region). The differential resistance r_text{diff} at a point P is the inverse slope of the line tangent to the graph at that pointr_text{diff} = frac {Delta v}{Delta i} = frac {v_2 - v_1}{i_2 - i_1} Since Delta v;>;0 and Delta i < 0, at point P r_text{diff} < 0.| width2 = 230| image3 = Negative static resistance definition.svg| caption3 = Fig. 3: I–V curve of a power source. In the 2nd quadrant (red region) current flows out of the positive terminal, so electric power flows out of the device into the circuit. For example at point P, v < 0 and i > 0, soR_text{static} = frac{v}{i} < 0 | width3 = 152| image4 = Active negative resistance definition.svg| caption4 = Fig. 4: I–V curve of a negative linear or “active” resistanceBOOK , In some of these graphs, the curve is reflected in the vertical axis so the negative resistance region appears to have positive slope. (AR, red). It has negative differential resistance and negative static resistance (is active):R = frac{Delta v}{Delta i} = frac{v}{i} < 0| width4 = 187}}

Operation

One way in which the different types of resistance can be distinguished is in the directions of current and electric power between a circuit and an electronic component. The illustrations below, with a rectangle representing the component attached to a circuit, summarize how the different types work:{|

v and current i variables in an electrical component must be defined according to the passive sign convention; positive conventional current is defined to enter the positive voltage terminal; this means power P flowing from the circuit into the component is defined to be positive, while power flowing from the component into the circuit is negative. This applies to both DC and AC current. The diagram shows the directions for positive values of the variables. >

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| In a positive static resistance, R_text{static};=;v/i;>;0, so v and i have the same sign.BOOK , , Therefore, from the passive sign convention above, conventional current (flow of positive charge) is through the device from the positive to the negative terminal, in the direction of the electric fieldE (decreasing potential). P = vi;>;0 so the charges lose potential energy doing work on the device, and electric power flows from the circuit into the device, where it is converted to heat or some other form of energy (yellow). If AC voltage is applied, v and i periodically reverse direction, but the instantaneous i always flows from the higher potential to the lower potential. || (File:Electric load animation 2.gif|140px)| In a power source, R_text{static} = v/i; 0 so the CCNR is stable for{{Equation box 1 |indent =:|cellpadding = 0 |border = 1 |border colour = black |background colour = transparent|equation = R_L;>;r.}}

• In a VCNR (N-type) negative resistance, the conductance function G_N = 1/R_N is single-valued. Therefore, stability is determined by the poles of the admittance equation Y_L(jomega) + Y_N(jomega) = 0. For this reason the VCNR is sometimes referred to as a negative conductance.{{pb}}As above, for nonreactive circuits a sufficient condition for stability is that the total conductance in the circuit is positive Y_L + Y_N = G_L + G_N = frac{1}{R_L} + frac{1}{R_N} = frac{1}{R_L} + frac{1}{-r} > 0 frac{1}{R_L} > frac{1}{r} so the VCNR is stable for

{{Equation box 1 |indent =: |cellpadding = 0 |border = 1 |border colour = black |background colour = transparent|equation = R_L < r.}} For general negative resistance circuits with reactance, the stability must be determined by standard tests like the Nyquist stability criterion.BOOK

Operating regions and applications

For simple nonreactive negative resistance devices with R_N;=;-r and X_N;=;0 the different operating regions of the device can be illustrated by load lines on the I–V curve (see graphs).{{multiple image| align = right| direction = horizontal| image1 = Negative resistance stability regions VCNR.svg| caption1 = VCNR (N type) load lines and stability regions| image2 = Negative resistance stability regions CCNR.svg| caption2 = CCNR (S type) load lines and stability regions| width = 180}}The DC load line (DCL) is a straight line determined by the DC bias circuit, with equation V = V_S - IR where V_S is the DC bias supply voltage and R is the resistance of the supply. The possible DC operating point(s) (Q points) occur where the DC load line intersects the I–V curve. For stability

• VCNRs require a low impedance bias {{nowrap|(R;;r)}} such as a current source, or voltage source in series with a high resistance.

The AC load line (L1 − L3) is a straight line through the Q point whose slope is the differential (AC) resistance R_L facing the device. Increasing R_L rotates the load line counterclockwise. The circuit operates in one of three possible regions (see diagrams), depending on R_L.

• Stable region (green) (illustrated by line L1): When the load line lies in this region, it intersects the I–V curve at one point Q1. For nonreactive circuits it is a stable equilibrium (poles in the LHP) so the circuit is stable. Negative resistance amplifiers operate in this region. However, due to hysteresis, with an energy storage device like a capacitor or inductor the circuit can become unstable to make a nonlinear relaxation oscillator (astable multivibrator) or a monostable multivibrator.Gottlieb 1997 Practical Oscillator Handbook, pp. 105–108 {{webarchive|url=https://web.archive.org/web/20160515053022books.google.com/books?id=e_oZ69GAuxAC |date=2016-05-15 }}
  • VCNRs are stable when R_L < r.
  • CCNRs are stable when R_L > r.
• Unstable point (Line L2): When R_L = r the load line is tangent to the I–V curve. The total differential (AC) resistance of the circuit is zero (poles on the jω axis), so it is unstable and with a tuned circuit can oscillate. Linear oscillators operate at this point. Practical oscillators actually start in the unstable region below, with poles in the RHP, but as the amplitude increases the oscillations become nonlinear, and due to eventual passivity the negative resistance r decreases with increasing amplitude, so the oscillations stabilize at an amplitude where r = R_L.
• Bistable region (red) (illustrated by line L3): In this region the load line can intersect the I–V curve at three points. The center point (Q1) is a point of unstable equilibrium (poles in the RHP), while the two outer points, Q2 and Q3 are stable equilibria. So with correct biasing the circuit can be bistable, it will converge to one of the two points Q2 or Q3 and can be switched between them with an input pulse. Switching circuits like flip-flops (bistable multivibrators) and Schmitt triggers operate in this region.
  • VCNRs can be bistable when R_L > r
  • CCNRs can be bistable when R_L < r

Active resistors – negative resistance from feedback

{{multiple image| align = right| direction = horizontal| header =| image1 = Active negative resistance - voltage controlled.svg| width1 = 150| image2 = Active negative resistance - current controlled.svg| width2 = 150| image3 = Negative resistance vs loop gain.svg| width3 = 150| footer = Typical I–V curves of “active” negative resistances:BOOK , , fig. 20.20 N-type (left), and S-type (center), generated by feedback amplifiers. These have negative differential resistance (red region) and produce power (grey region). Applying a large enough voltage or current of either polarity to the port moves the device into its nonlinear region where saturation of the amplifier causes the differential resistance to become positive (black portion of curve), and above the supply voltage rails pm V_S the static resistance becomes positive and the device consumes power. The negative resistance depends on the loop gain Abeta (right).}}(File:Negative resistance by positive feedback.svg|thumb|upright=1.2|An example of an amplifier with positive feedback that has negative resistance at its input. The input current i isi = frac{v - Av}{R_1} + frac{v}{R_text{in}}so the input resistance isR = frac{v}{i} = frac{R_1}{1 + R_1/R_text{in} - A}.If A > 1 + R_1/R_text{in} it will have negative input resistance.)In addition to the passive devices with intrinsic negative differential resistance above, circuits with amplifying devices like transistors or op amps can have negative resistance at their ports. The input or output impedance of an amplifier with enough positive feedback applied to it can be negative.BOOK R_text{if} = frac {R_text{i} }{1 - Abeta} So if the loop gain Abeta is greater than one, R_{if} will be negative. The circuit acts like a “negative linear resistor“BOOK , BOOK frac{Delta v}{Delta i} = {v over i} = R_text{if} < 0 and thus obeys Ohm’s law as if it had a negative value of resistance −R,BOOK , over its linear range (such amplifiers can also have more complicated negative resistance I–V curves that do not pass through the origin).In circuit theory these are called “active resistors”. Applying a voltage across the terminals causes a proportional current out of the positive terminal, the opposite of an ordinary resistor. For example, connecting a battery to the terminals would cause the battery to charge rather than discharge.Considered as one-port devices, these circuits function similarly to the passive negative differential resistance components above, and like them can be used to make one-port amplifiers and oscillators with the advantages that:

• because they are active devices they do not require an external DC bias to provide power, and can be DC coupled,
• the amount of negative resistance can be varied by adjusting the loop gain,
• they can be linear circuit elements; if operation is confined to the straight segment of the curve near the origin the voltage is proportional to the current, so they do not cause harmonic distortion.

The I–V curve can have voltage-controlled (“N” type) or current-controlled (“S” type) negative resistance, depending on whether the feedback loop is connected in “shunt” or “series”.Negative reactances (below) can also be created, so feedback circuits can be used to create “active” linear circuit elements, resistors, capacitors, and inductors, with negative values. They are widely used in active filters because they can create transfer functions that cannot be realized with positive circuit elements.CONFERENCE , frequency dependent negative resistance (FDNR), and generalized immittance converter (GIC).BOOK ,

Feedback oscillators

If an LC circuit is connected across the input of a positive feedback amplifier like that above, the negative differential input resistance R_text{if} can cancel the positive loss resistance r_text{loss} inherent in the tuned circuit.this property was often called “resistance neutralization” in the days of vacuum tubes, see JOURNAL , and Ch. 3: “Resistance Neutralization” in BOOK , If R_text{if};=;-r_text{loss} this will create in effect a tuned circuit with zero AC resistance (poles on the jω axis). Spontaneous oscillation will be excited in the tuned circuit at its resonant frequency, sustained by the power from the amplifier. This is how feedback oscillators such as Hartley or Colpitts oscillators work.BOOK , , Sec. 3 Negative Resistance Oscillators, pp. 9–10, 14, All linear oscillator circuits have negative resistance although in most feedback oscillators the tuned circuit is an integral part of the feedback network, so the circuit does not have negative resistance at all frequencies but only near the oscillation frequency.Gottlieb 1997, Practical Oscillator Handbook, p. 84 {{webarchive|url=https://web.archive.org/web/20160515053022books.google.com/books?id=e_oZ69GAuxAC |date=2016-05-15 }}

Q enhancement

A tuned circuit connected to a negative resistance which cancels some but not all of its parasitic loss resistance (so |R_text{if}|;;0. Applying a positive current to a negative capacitance will cause it to discharge; its voltage will decrease. Similarly, a negative inductance will have an I–V characteristic and impedance Z_text{L}(jomega) ofv = -L {di over dt} qquadqquad Z_L = -jomega L A circuit having negative capacitance or inductance can be used to cancel unwanted positive capacitance or inductance in another circuit. NIC circuits were used to cancel reactance on telephone cables.There is also another way of looking at them. In a negative capacitance the current will be 180° opposite in phase to the current in a positive capacitance. Instead of leading the voltage by 90° it will lag the voltage by 90°, as in an inductor. Therefore, a negative capacitance acts like an inductance in which the impedance has a reverse dependence on frequency ω; decreasing instead of increasing like a real inductance Similarly a negative inductance acts like a capacitance that has an impedance which increases with frequency. Negative capacitances and inductances are “non-Foster” circuits which violate Foster’s reactance theorem.BOOK , This would allow the creation of small compact antennas that would have broad bandwidth, exceeding the Chu–Harrington limit.

Oscillators

File:Ganna gjenerators M31102-1.jpg|thumb|upright=0.8|An oscillator consisting of a Gunn diode inside a cavity resonator. The negative resistance of the diode excites microwave oscillations in the cavity, which radiate through the aperture into a waveguidewaveguideNegative differential resistance devices are widely used to make electronic oscillators.CONFERENCE , with a DC source to bias the device into its negative resistance region and provide power.BOOK , A resonator such as an LC circuit is “almost” an oscillator; it can store oscillating electrical energy, but because all resonators have internal resistance or other losses, the oscillations are damped and decay to zero. The negative resistance cancels the positive resistance of the resonator, creating in effect a lossless resonator, in which spontaneous continuous oscillations occur at the resonator’s resonant frequency.

Uses

Negative resistance oscillators are mainly used at high frequencies in the microwave range or above, since feedback oscillators function poorly at these frequencies. Microwave diodes are used in low- to medium-power oscillators for applications such as radar speed guns, and local oscillators for satellite receivers. They are a widely used source of microwave energy, and virtually the only solid-state source of millimeter waveBOOK The negative resistance oscillator model is not limited to one-port devices like diodes but can also be applied to feedback oscillator circuits with two port devices such as transistors and tubes.BOOK , BOOK , In addition, in modern high frequency oscillators, transistors are increasingly used as one-port negative resistance devices like diodes. At microwave frequencies, transistors with certain loads applied to one port can become unstable due to internal feedback and show negative resistance at the other port. So high frequency transistor oscillators are designed by applying a reactive load to one port to give the transistor negative resistance, and connecting the other port across a resonator to make a negative resistance oscillator as described below.

Gunn diode oscillator

{{multiple image| align = right| direction = horizontal| image1 = Gunn diode oscillator circuit.svg| caption1 = Gunn diode oscillator circuit| width1 = 150| image2 = Gunn diode oscillator AC circuit.svg| caption2 = AC equivalent circuit| width2 = 102| footer =}}File:Negative resistance oscillator load lines.svg|thumb|upright=1.3|Gunn diode oscillator load lines.DCL: DC load line, which sets the Q point.SSL: negative resistance during startup while amplitude is small. Since r; r. It can be seen that the reflection amplifier can have unlimited gain, approaching infinity as R_1 approaches the point of oscillation at r. This is a characteristic of all NR amplifiers, contrasting with the behavior of two-port amplifiers, which generally have limited gain but are often unconditionally stable. In practice the gain is limited by the backward “leakage” coupling between circulator ports.Masers and parametric amplifiers are extremely low noise NR amplifiers that are also implemented as reflection amplifiers; they are used in applications like radio telescopes.

Switching circuits

Negative differential resistance devices are also used in switching circuits in which the device operates nonlinearly, changing abruptly from one state to another, with hysteresis. The advantage of using a negative resistance device is that a relaxation oscillator, flip-flop or memory cell can be built with a single active device, whereas the standard logic circuit for these functions, the Eccles-Jordan multivibrator, requires two active devices (transistors). Three switching circuits built with negative resistances are

• Astable multivibrator – a circuit with two unstable states, in which the output periodically switches back and forth between the states. The time it remains in each state is determined by the time constant of an RC circuit. Therefore, it is a relaxation oscillator, and can produce square waves or triangle waves.
• Monostable multivibrator – is a circuit with one unstable state and one stable state. When in its stable state a pulse is applied to the input, the output switches to its other state and remains in it for a period of time dependent on the time constant of the RC circuit, then switches back to the stable state. Thus the monostable can be used as a timer or delay element.
• Bistable multivibrator or flip flop – is a circuit with two stable states. A pulse at the input switches the circuit to its other state. Therefore, bistables can be used as memory circuits, and digital counters.

Other applications

Neuronal models

Some instances of neurons display regions of negative slope conductances (RNSC) in voltage-clamp experiments.JOURNAL

History

Negative resistance was first recognized during investigations of electric arcs, which were used for lighting during the 19th century.BOOK , In 1881 Alfred NiaudetA. Niaudet, La Lumiere Electrique, No. 3, 1881, p. 287, cited in Encyclopædia Britannica, 11th Ed., Vol. 16, p. 660 had observed that the voltage across arc electrodes decreased temporarily as the arc current increased, but many researchers thought this was a secondary effect due to temperature. The term “negative resistance” was applied by some to this effect, but the term was controversial because it was known that the resistance of a passive device could not be negative.EB1911, Lighting, 16, Garcke, Emile, Emile Garcke, 651–673;see pages 660-661, JOURNAL , Frith and Rodgers in 1896JOURNAL

Arc transmitters

George Francis FitzGerald first realized in 1892 that if the damping resistance in a resonant circuit could be made zero or negative, it would produce continuous oscillations.G. Fitzgerald, On the Driving of Electromagnetic Vibrations by Electromagnetic and Electrostatic Engines, read at the January 22, 1892 meeting of the Physical Society of London, in BOOK , In the same year Elihu Thomson built a negative resistance oscillator by connecting an LC circuit to the electrodes of an arc,BOOK , BOOK , perhaps the first example of an electronic oscillator. William Duddell, a student of Ayrton at London Central Technical College, brought Thomson’s arc oscillator to public attention. Due to its negative resistance, the current through an arc was unstable, and arc lights would often produce hissing, humming, or even howling noises. In 1899, investigating this effect, Duddell connected an LC circuit across an arc and the negative resistance excited oscillations in the tuned circuit, producing a musical tone from the arc. To demonstrate his invention Duddell wired several tuned circuits to an arc and played a tune on it. Duddell’s “singing arc” oscillator was limited to audio frequencies. However, in 1903 Danish engineers Valdemar Poulsen and P. O. Pederson increased the frequency into the radio range by operating the arc in a hydrogen atmosphere in a magnetic field,CONFERENCE, Valdemar, Poulsen, System for producing continuous electric oscillations, Transactions of the International Electrical Congress, St. Louis, 1904, Vol. 2, 963–971, J. R. Lyon Co., 12 September 1904,books.google.com/books?id=JHgSAAAAYAAJ&pg=PA963, 22 September 2013, live,books.google.com/books?id=JHgSAAAAYAAJ&pg=PA963," title="web.archive.org/web/20131009040125books.google.com/books?id=JHgSAAAAYAAJ&pg=PA963,">web.archive.org/web/20131009040125books.google.com/books?id=JHgSAAAAYAAJ&pg=PA963, 9 October 2013, inventing the Poulsen arc radio transmitter, which was widely used until the 1920s.

Vacuum tubes

By the early 20th century, although the physical causes of negative resistance were not understood, engineers knew it could generate oscillations and had begun to apply it. Heinrich Barkhausen in 1907 showed that oscillators must have negative resistance. Ernst Ruhmer and Adolf Pieper discovered that mercury vapor lamps could produce oscillations, and by 1912 AT&T had used them to build amplifying repeaters for telephone lines.In 1918 Albert Hull at GE discovered that vacuum tubes could have negative resistance in parts of their operating ranges, due to a phenomenon called secondary emission.JOURNAL The negative impedance converter originated from work by Marius Latour around 1920.JOURNAL

Solid state devices

Negative differential resistance in semiconductors was observed around 1909 in the first point-contact junction diodes, called cat’s whisker detectors, by researchers such as William Henry EcclesBOOK , JOURNAL The first person to exploit negative resistance diodes practically was Russian radio researcher Oleg Losev, who in 1922 discovered negative differential resistance in biased zincite (zinc oxide) point contact junctions.JOURNAL , BOOK , Lee, Thomas H. (2004) The Design of CMOS Radio-Frequency Integrated Circuits, 2nd Ed., p. 20 He used these to build solid-state amplifiers, oscillators, and amplifying and regenerative radio receivers, 25 years before the invention of the transistor.JOURNAL , and “The Crystodyne Principle”, pp. 294–295 Later he even built a superheterodyne receiver. However his achievements were overlooked because of the success of vacuum tube technology. After ten years he abandoned research into this technology (dubbed “Crystodyne” by Hugo Gernsback), and it was forgotten.The first widely used solid-state negative resistance device was the tunnel diode, invented in 1957 by Japanese physicist Leo Esaki.JOURNAL

Notes

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References

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Further reading

• BOOK, Gottlieb, Irving M., Practical Oscillator Handbook, Elsevier, 1997,books.google.com/books?id=e_oZ69GAuxAC&q=%22negative+resistance&pg=PA75, 978-0080539386, How negative differential resistance devices work in oscillators.
• BOOK, Hong, Sungook, Wireless: From Marconi’s Black-Box to the Audion, MIT Press, 2001, USA,monoskop.org/images/f/f4/Hong_Sungook_Wireless_From_Marconis_Black-Box_to_the_Audion.pdf, 978-0262082983, , ch. 6 Account of discovery of negative resistance and its role in early radio.
• ENCYCLOPEDIA, Snelgrove, Martin, Negative resistance circuits, AccessScience Online Encyclopedia, McGraw-Hill, 2008, 10.1036/1097-8542.446710,www.accessscience.com/content/negative-resistance-circuits/446710, May 17, 2012, Elementary one-page introduction to negative resistance.

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