A
semiconductor curve tracer is a specialised piece of
electronic test equipmentElectronic test equipment is used to create signals and capture responses from electronic Devices Under Test . In this way, the proper operation of the DUT can be proven or faults in the device can be traced and repaired...
used to analyse the characteristics of discrete
semiconductor deviceSemiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide. Semiconductor devices have replaced thermionic devices in most applications...
s such as
diodeIn electronics a diode is a two-terminal electronic component which conducts electric current asymmetrically or unidirectionally; that is, it conducts current more easily in one direction than in the opposite direction. The term usually refers to a semiconductor diode, the most common type today,...
s,
transistorA transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's...
s, and
thyristorThe thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. They act as bistable switches, conducting when their gate receives a current pulse, and continue to conduct for as long as they are forward biased .Some sources define silicon controlled...
s. Based on an
oscilloscopeAn oscilloscope is a type of electronic test instrument that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences plotted as a function of time or of some other voltage...
, the device also contains voltage and
current sourceA current source is an electrical or electronic device that delivers or absorbs electric current. A current source is the dual of a voltage source...
s that can be used to stimulate the
device under testDevice under test , also known as unit under test , is a term commonly used to refer to a manufactured product undergoing testing.- In semiconductor testing :...
(DUT).
The basic operating principle of the device is to apply a swept (automatically varying) voltage to the main terminals of the DUT while measuring the amount of current that the device permits to flow.
A
semiconductor curve tracer is a specialised piece of
electronic test equipmentElectronic test equipment is used to create signals and capture responses from electronic Devices Under Test . In this way, the proper operation of the DUT can be proven or faults in the device can be traced and repaired...
used to analyse the characteristics of discrete
semiconductor deviceSemiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide. Semiconductor devices have replaced thermionic devices in most applications...
s such as
diodeIn electronics a diode is a two-terminal electronic component which conducts electric current asymmetrically or unidirectionally; that is, it conducts current more easily in one direction than in the opposite direction. The term usually refers to a semiconductor diode, the most common type today,...
s,
transistorA transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's...
s, and
thyristorThe thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. They act as bistable switches, conducting when their gate receives a current pulse, and continue to conduct for as long as they are forward biased .Some sources define silicon controlled...
s. Based on an
oscilloscopeAn oscilloscope is a type of electronic test instrument that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences plotted as a function of time or of some other voltage...
, the device also contains voltage and
current sourceA current source is an electrical or electronic device that delivers or absorbs electric current. A current source is the dual of a voltage source...
s that can be used to stimulate the
device under testDevice under test , also known as unit under test , is a term commonly used to refer to a manufactured product undergoing testing.- In semiconductor testing :...
(DUT).
Operation
The basic operating principle of the device is to apply a swept (automatically varying) voltage to the main terminals of the DUT while measuring the amount of current that the device permits to flow. This so-called V-I (voltage versus current) graph is displayed on an oscilloscope screen. The operator can control the maximum amount of voltage applied to the device, the polarity of the voltage applied (including the automatic application of both positive and negative polarities), and the load resistance inserted in series with the device.
For two terminal devices (such as diodes and
DIACThe DIAC, or diode for alternating current, is a trigger diode that conducts current only after its breakdown voltage has been exceeded momentarily. When this occurs, the resistance of the diode abruptly decreases, leading to a sharp decrease in the voltage drop across the diode and, usually, a...
s), this is sufficient to fully characterize the device. The curve tracer can display all of the interesting parameters such as the diode's forward voltage,
reverse leakage currentReverse leakage current in a semiconductor device is the current from that semiconductor device when the device is reverse biased.The term it particularly applicable to is mostly semiconductor junctions diode....
, reverse breakdown voltage, and so on. For triggerable devices such as DIACs, the forward and reverse trigger voltages will be clearly displayed. The discontinuity caused by
negative resistanceNegative resistance is a property of some electric circuits where an increase in the current entering a port, results in a decreased voltage across the same port. This is in contrast to a simple ohmic resistor, which exhibits an increase in voltage under the same conditions. Negative resistors...
devices (such as
tunnel diodeA tunnel diode or Esaki diode is a type of semiconductor diode which is capable of very fast operation, well into the microwave frequency region, by using quantum mechanical effects....
s) can also be seen.
The main terminal voltage can often be swept up to several thousand volts with load currents of tens of amps available at lower voltages.
Three-terminal devices require an additional connection; this is usually supplied from a stepped voltage or current source attached to the control terminal of the DUT. By sweeping through the full range of main terminal voltages with each step of the control signal, a family of V-I curves can be generated. This family of curves makes it very easy to determine the gain of a transistor or the trigger voltage of a thyristor or
TRIACA TRIAC, or Triode for Alternating Current is an electronic component approximately equivalent to two silicon-controlled rectifiers joined in inverse parallel and with their gates connected together. The formal name for a TRIAC is bidirectional triode thyristor...
. For most devices, a stepped current is used. For field effect transistors, a stepped voltage is used instead.
Curve tracers usually contain convenient connection arrangements for two- or three-terminal DUTs, often in the form of sockets arranged to allow the plugging-in of the various common packages used for transistors and diodes. Most curve tracers also allow the simultaneous connection of two DUTs; in this way, two DUTs can be "matched" for optimum performance in circuits (such as
differential amplifierA differential amplifier is a type of electronic amplifier that multiplies the difference between two inputs by some constant factor .Many electronic devices use differential amplifiers internally....
s) which depend upon the close matching of device parameters. This can be seen in the image to the right where a toggle switch allows the rapid switching between the DUT on the left and the DUT on the right as the operator compared the respective curve families of the two devices.
Kelvin sensing
Curve tracers are usually supplied with various semiconductor device test fixture adapters
http://www.tek.com/site/ps/0,,76-15104-INTRO_EN,00.html that have
Kelvin sensingFour-terminal sensing , 4-wire sensing, or 4-point probes method is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make more accurate measurements than traditional two-terminal sensing...
.
History
Ironically enough, the original semiconductor curve tracers were originally based on
vacuum tubeIn electronics, a vacuum tube, electron tube , thermionic valve, or valve is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space...
circuits. The Scientific Test, Inc. Curve Tracer is unique in its differences from the Tektronix Model. The
TektronixTektronix, Inc. is a North American company best known for its test and measurement equipment such as oscilloscopes, logic analyzers, and video and mobile test protocol equipment. As of November 2007, Tektronix is a subsidiary of Danaher Corporation....
model 575 curve tracer shown in the gallery was a typical instrument of this generation. At this time, the available semiconductor devices simply didn't have enough performance to generate the test waveforms adequate to characterise themselves.
Nowadays, curve tracers are entirely
solid stateSolid state may refer to:In science:*Solid-state chemistry*Solid-state physics*Solid-state laser*Solid matterIn electronics:*Solid state , circuits built of solid materials...
(with the possible exception of the
CRTThe cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen...
) and are substantially automated to ease the workload of the operator, automatically capture data, and assure the safety of the curve tracer as well as the DUT.
- CircuitMaster 4000M
- Counterfeit IC Detector
- System 8 Range of V-I Testers
Availability
The Agilent B1505A is a new product that is orderable starting April 1, 2009.
Scientific Test,Inc. based in Richardson,TX has curve tracers available in current production with ongoing support. Scientific Test, Inc. has details of products at
http://www.scitest.com
This Tektronix page has details of the 370B and 371B models,
http://www2.tek.com/cmswpt/psdetails.lotr?ct=PS&cs=psu&ci=13558&lc=EN. Both models have been discontinued.
Reconditioned curve tracers may still be obtained from various suppliers of used test equipment.
Safety
Curve tracers are capable of generating lethal voltages and currents and so pose an
electrocutionAn electric shock can occur upon contact of a human body with any source of voltage high enough to cause sufficient current through the muscles or hair. The minimum current a human can feel is thought to be about 1 milliampere ....
hazard for the operator. Modern curve tracers often contain mechanical shields and
interlocksInterlocking is a method of preventing undesired states in a state machine, which in a general sense can include any electrical, electronic, or mechanical device or system....
that make it more difficult for the operator to come into contact with hazardous voltages or currents. The DUTs can also become hot during operation, posing a
burnA burn is a type of injury that may be caused by heat, electricity, chemicals, light, radiation, or friction. Burns can be highly variable in terms of the tissue affected, the severity, and resultant complications. Muscle, bone, blood vessel, dermal and epidermal tissue can all be damaged with...
hazard to the operator.
External links