In
electronic instrumentation
Instrumentation is a collective term for measuring instruments, used for indicating, measuring, and recording physical quantities. It is also a field of study about the art and science about making measurement instruments, involving the related ...
and
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, Scalar potential, potential fields, Seismic tomograph ...
, a time-to-digital converter (TDC) or time digitizer (TD) is a device for recognizing
events and providing a digital representation of the
time
Time is the continuous progression of existence that occurs in an apparently irreversible process, irreversible succession from the past, through the present, and into the future. It is a component quantity of various measurements used to sequ ...
they occurred. For example, a TDC might output the
time of arrival for each incoming pulse. Some applications wish to measure the time interval between two events rather than some notion of an absolute time, and the digitizer is then used to measure a time interval and convert it into digital (binary) output. In some cases,
an
interpolating TDC is also called a time counter (TC).
When TDCs are used to determine the time interval between two signal pulses (known as start and stop pulse), measurement is started and stopped when the
rising or falling edge of a signal pulse crosses a set threshold. This pattern is seen in many physical experiments, like
time-of-flight and lifetime measurements in
atomic and
high energy physics
Particle physics or high-energy physics is the study of fundamental particles and forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the stu ...
, experiments that involve
laser ranging and electronic research involving the testing of
integrated circuits
An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...
and high-speed data transfer.
Several methods exist for time digitization. Some types allow for nanosecond accuracy, while other are capable of picosecond accuracy (see Coarse measurement and Fine measurement sections below, respectively).
Application
TDCs are used to
timestamp
A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolu ...
events and measure time differences between events, especially where picosecond precision and high accuracy is required, such as the measurement of events in
high energy physics
Particle physics or high-energy physics is the study of fundamental particles and forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the stu ...
experiment
An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs whe ...
s, where particles (e.g. electrons, photons, and ions) are detected.
Another application is cost-effective and non-mechanical water
flow metering by measuring the time difference between ultrasound pulses that travel through the flow and arrive at different times depending on the flow speed and direction.
In an all-digital
phase-locked loop
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is fixed relative to the phase of an input signal. Keeping the input and output phase in lockstep also implies keeping the input and ou ...
(ADPLL), a TDC measures the phase shift and its result is used to adjust the
digital controlled oscillator (DCO).
Coarse measurement

If the required time resolution is not high (nanosecond resolution?), then counters can be used to make the conversion.
Basic counter
In its simplest implementation, a TDC is simply a high-
frequency
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
counter that increments every clock cycle. The current contents of the counter represents the current time. When an event occurs, the counter's value is captured in an output register.
In that approach, the measurement is an integer number of clock cycles, so the measurement is quantized to a clock period. To get finer resolution, a faster clock is needed. The accuracy of the measurement depends upon the stability of the clock frequency.
Typically a TDC uses a
crystal oscillator
A crystal oscillator is an electronic oscillator Electrical circuit, circuit that uses a piezoelectricity, piezoelectric crystal as a frequency selective surface, frequency-selective element. The oscillator frequency is often used to keep trac ...
reference frequency for good long term stability. High stability crystal oscillators are usually relative low frequency such as 10 MHz (or 100 ns resolution). To get better resolution, a
phase-locked loop
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is fixed relative to the phase of an input signal. Keeping the input and output phase in lockstep also implies keeping the input and ou ...
frequency multiplier can be used to generate a faster clock. One might, for example, multiply the crystal reference oscillator by 100 to get a clock rate of 1 GHz (1 ns resolution).
Counter technology
High clock rates impose additional design constraints on the counter: if the clock period is short, it is difficult to update the count. Binary counters, for example, need a fast carry architecture because they essentially add one to the previous counter value. A solution is using a hybrid counter architecture. A
Johnson counter, for example, is a fast non-binary counter. It can be used to count very quickly the low order count; a more conventional binary counter can be used to accumulate the high order count. The fast counter is sometime called a
prescaler.
The speed of counters fabricated in
CMOS
Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss
", , ) is a type of MOSFET, metal–oxide–semiconductor field-effect transistor (MOSFET) semiconductor device fabrication, fabrication process that uses complementary an ...
-technology is limited by the capacitance between the gate and the channel and by the resistance of the channel and the signal traces. The product of both is the cut-off-frequency. Modern chip technology allows multiple metal layers and therefore coils with a large number of windings to be inserted into the chip.
This allows designers to peak the device for a specific
frequency
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
, which may lie above the cut-off-frequency of the original transistor.
A peaked variant of the Johnson counter is the
traveling-wave counter which also achieves sub-cycle resolution. Other methods to achieve sub-cycle resolution include
analog-to-digital converter
In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a Digital signal (signal processing), digi ...
s and
vernier Johnson counters.
Measuring a time interval

In most situations, the user does not want to just capture an absolute time that an event occurs, but wants to measure a time interval, i.e the time between a start event and a stop event.
That can be done by measuring an arbitrary time of both the start and stop events and subtracting. The measurement can be off by two counts.
The subtraction can be avoided if the counter is held at zero until the start event, counts during the interval, and then stops counting after the stop event.
Coarse counters base on a
reference clock with signals generated at a stable
frequency
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
.
When the start signal is detected the
counter starts counting clock signals and terminates counting after the stop signal is detected. The time interval
between start and stop is then
:
with
, the number of counts and
, the period of the
reference clock.
Statistical counter
Since start, stop and
clock signal
In electronics and especially synchronous digital circuits, a clock signal (historically also known as ''logic beat'') is an electronic logic signal (voltage or current) which oscillates between a high and a low state at a constant frequency and ...
are asynchronous, there is a uniform
probability distribution
In probability theory and statistics, a probability distribution is a Function (mathematics), function that gives the probabilities of occurrence of possible events for an Experiment (probability theory), experiment. It is a mathematical descri ...
of the start and stop signal-times between two subsequent clock pulses. This detuning of the start and stop signal from the clock pulses is called
quantization error
Quantization, in mathematics and digital signal processing, is the process of mapping input values from a large set (often a continuous set) to output values in a (countable) smaller set, often with a finite number of elements. Rounding and ...
.
For a series of measurements on the same constant and asynchronous time interval one measures two different numbers of counted clock pulses
and
(see picture). These occur with
probabilities
Probability is a branch of mathematics and statistics concerning Event (probability theory), events and numerical descriptions of how likely they are to occur. The probability of an event is a number between 0 and 1; the larger the probab ...
:
:
with
the
fractional part
The fractional part or decimal part of a non‐negative real number x is the excess beyond that number's integer part. The latter is defined as the largest integer not greater than , called ''floor'' of or \lfloor x\rfloor. Then, the fractional ...
of
. The value for the time interval is then obtained by
:
Measuring a time interval using a coarse counter with the averaging method described above is relatively time consuming because of the many repetitions that are needed to determine the probabilities
and
. In comparison to the other methods described later on, a coarse counter has a very limited resolution (1 ns in case of a 1 GHz
reference clock), but satisfies with its theoretically unlimited measuring range.
Fine measurement
In contrast to the coarse counter in the previous section, fine measurement methods with much better accuracy (picosecond resolution?), but far smaller measuring range are presented here.
Analogue methods like time interval stretching or double conversion as well as
digital
Digital usually refers to something using discrete digits, often binary digits.
Businesses
*Digital bank, a form of financial institution
*Digital Equipment Corporation (DEC) or Digital, a computer company
*Digital Research (DR or DRI), a software ...
methods like tapped delay lines and the Vernier method are under examination. Though the
analogue methods still obtain better accuracies,
digital
Digital usually refers to something using discrete digits, often binary digits.
Businesses
*Digital bank, a form of financial institution
*Digital Equipment Corporation (DEC) or Digital, a computer company
*Digital Research (DR or DRI), a software ...
time interval measurement is often preferred due to its flexibility in
integrated circuit
An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...
technology and its robustness against external perturbations like temperature changes.
The counter implementation's accuracy is limited by the clock frequency. If time is measured by whole counts, then the resolution is limited to the clock period. For example, a 10 MHz clock has a resolution of 100 ns. To get resolution finer than a clock period, there are time interpolation circuits. These circuits measure the fraction of a clock period: that is, the time between a clock event and the event being measured. The interpolation circuits often require a significant amount of time to perform their function; consequently, the TDC needs a quiet interval before the next measurement.
Ramp interpolator
When counting is not feasible because the clock rate would be too high, analog methods can be used. Analog methods are often used to measure intervals that are between 10 and 200 ns. These methods often use a capacitor that is charged during the interval being measured.
Initially, the capacitor is discharged to zero volts. When the start event occurs, the capacitor is charged with a constant current ''I''
1; the constant current causes the voltage ''v'' on the capacitor to increase linearly with time. The rising voltage is called the fast ramp. When the stop event occurs, the charging current is stopped. The voltage on the capacitor ''v'' is directly proportional to the time interval ''T'' and can be measured with an
analog-to-digital converter
In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a Digital signal (signal processing), digi ...
(ADC). The resolution of such a system is in the range of 1 to 10 ps.
Although a separate ADC can be used, the ADC step is often integrated into the interpolator. A second constant current ''I''
2 is used to discharge the capacitor at a constant but much slower rate (the slow ramp). The slow ramp might be 1/1000 of the fast ramp. This discharge effectively "stretches" the time interval;
[ stating, "Effectively, the interpolator magnifies the interpolation or uncertainty interval by the ratio of the charge and discharge currents."] it will take 1000 times as long for the capacitor to discharge to zero volts. The stretched interval can be measured with a counter. The measurement is similar to a
dual-slope analog converter.
The dual-slope conversion can take a long time: a thousand or so clock ticks in the scheme described above. That limits how often a measurement can be made (
dead time). Resolution of 1 ps with a 100 MHz (10 ns) clock requires a stretch ratio of 10,000 and implies a conversion time of 150 μs.
To decrease the conversion time, the interpolator circuit can be used twice in a residual interpolator technique.
The fast ramp is used initially as above to determine the time. The slow ramp is only at 1/100. The slow ramp will cross zero at some time during the clock period. When the ramp crosses zero, the fast ramp is turned on again to measure the crossing time (''t''
residual). Consequently, the time can be determined to 1 part in 10,000.
Interpolators are often used with a stable system clock. The start event is asynchronous, but the stop event is a following clock.
For convenience, imagine that the fast ramp rises exactly 1 volt during a 100 ns clock period. Assume the start event occurs at 67.3 ns after a clock pulse; the fast ramp integrator is triggered and starts rising. The asynchronous start event is also routed through a synchronizer that takes at least two clock pulses. By the next clock pulse, the ramp has risen to .327 V. By the second clock pulse, the ramp has risen to 1.327 V and the synchronizer reports the start event has been seen. The fast ramp is stopped and the slow ramp starts. The synchronizer output can be used to capture system time from a counter. After 1327 clocks, the slow ramp returns to its starting point, and interpolator knows that the event occurred 132.7 ns before the synchronizer reported.
The interpolator is actually more involved because there are synchronizer issues and current switching is not instantaneous. Also, the interpolator must calibrate the height of the ramp to a clock period.
Vernier
Vernier interpolator
The vernier method is more involved. The method involves a triggerable oscillator and a coincidence circuit. At the event, the integer clock count is stored and the oscillator is started. The triggered oscillator has a slightly different frequency than the clock oscillator. For sake of argument, say the triggered oscillator has a period that is 1 ns faster than the clock. If the event happened 67 ns after the last clock, then the triggered oscillator transition will slide by −1 ns after each subsequent clock pulse. The triggered oscillator will be at 66 ns after the next clock, at 65 ns after the second clock, and so forth. A coincidence detector looks for when the triggered oscillator and the clock transition at the same time, and that indicates the fraction time that needs to be added.
The interpolator design is more involved. The triggerable clock must be calibrated to clock. It must also start quickly and cleanly.
Vernier method
The Vernier method is a
digital
Digital usually refers to something using discrete digits, often binary digits.
Businesses
*Digital bank, a form of financial institution
*Digital Equipment Corporation (DEC) or Digital, a computer company
*Digital Research (DR or DRI), a software ...
version of the time stretching method. Two only slightly detuned
oscillators
Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...
(with
frequencies
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
and
) start their signals with the arrival of the start and the stop signal. As soon as the leading edges of the
oscillator
Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...
signals coincide the measurement ends and the number of periods of the oscillators (
and
respectively) lead to the original time interval
:
:
Since highly reliable
oscillators
Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...
with stable and accurate
frequency
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
are still quite a challenge one also realizes the vernier method via two tapped delay lines using two slightly different cell delay times
. This setting is called differential delay line or vernier delay line.
In the example presented here the first delay line affiliated with the start signal contains cells of
D-flip-flops with delay
which are initially set to transparent. During the transition of the start signal through one of those cells, the signal is delayed by
and the state of the flip-flop is sampled as transparent. The second delay line belonging to the stop signal is composed of a series of
non-inverting buffers with delay
. Propagating through its channel the stop signal latches the flip-flops of the start signal's delay line. As soon as the stop signal passes the start signal, the latter is stopped and all leftover flip-flops are sampled opaque. Analogous to the above case of the oscillators the wanted time interval
is then
:
with n the number of cells marked as transparent.
Digital delay-line based TDC

In general a digital delay-line based TDC,
also known as tapped delay line, contains a chain of cells (e.g. using
D-latches in the figure) with well defined delay times
. The start signal propagates through this chain and is successively delayed by each cell. The number of cells that the start signal propagated through when the stop signal happens will be the (
rounded) time interval between the start and stop signal divided by
.
Hybrid measurement

Counters can measure long intervals but have limited resolution. Interpolators have high resolution but they cannot measure long intervals. A hybrid approach can achieve both long intervals and high resolution.
The long interval can be measured with a counter. The counter information is supplemented with two time interpolators: one interpolator measures the (short) interval between the start event and a following clock event, and the second interpolator measure the interval between the stop event and a following clock event. The basic idea has some complications: the start and stop events are asynchronous, and one or both might happen close to a clock pulse. The counter and interpolators must agree on matching the start and end clock events. To accomplish that goal, synchronizers are used.
The common hybrid approach is the Nutt method. In this example the fine measurement circuit measures the time between start and stop pulse and the respective second nearest clock pulse of the coarse counter (''T''
start, ''T''
stop), detected by the synchronizer (see figure). Thus the wanted time interval is
:
with ''n'' the number of counter clock pulses and ''T''
0 the period of the coarse counter.
History
Time measurement has played a crucial role in the understanding of nature from the earliest times. Starting with sun, sand or water driven
clock
A clock or chronometer is a device that measures and displays time. The clock is one of the oldest Invention, human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, a ...
s we are able to use clocks today, based on the most precise
caesium
Caesium (IUPAC spelling; also spelled cesium in American English) is a chemical element; it has Symbol (chemistry), symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only f ...
resonators.
The first direct predecessor of a TDC was invented in the year 1942 by
Bruno Rossi for the measurement of
muon
A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of ''ħ'', but with a much greater mass. It is classified as a ...
lifetimes. It was designed as a time-to-amplitude-converter, constantly charging a
capacitor
In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...
during the measured time interval. The corresponding
voltage
Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), ...
is directly proportional to the time interval under examination.
While the basic concepts (like Vernier methods (
Pierre Vernier
Pierre Vernier (; 19 August 1580 at Ornans, Franche-Comté (at that time ruled by the Spanish Habsburgs, now part of France) – 14 September 1637, same location) was a mathematician and instrument inventor. He was the inventor and eponym o ...
1584-1638) and time stretching) of dividing time into measurable intervals are still up-to-date, the implementation changed a lot during the past 50 years. Starting with
vacuum tubes
A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...
and
ferrite pot-core transformers those ideas are implemented in complementary metal–oxide–semiconductor (
CMOS
Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss
", , ) is a type of MOSFET, metal–oxide–semiconductor field-effect transistor (MOSFET) semiconductor device fabrication, fabrication process that uses complementary an ...
) design today.
Errors
:
Some information from
Regarding even the fine measuring methods presented, there are still errors one may wish remove or at least to consider. Non-linearities of the time-to-digital conversion for example can be identified by taking a large number of measurements of a
poissonian distributed source (statistical code density test). Small deviations from the uniform distribution reveal the non-linearities.
Inconveniently the statistical code density method is quite sensitive to external temperature changes. Thus stabilizing
delay or
phase-locked loop
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is fixed relative to the phase of an input signal. Keeping the input and output phase in lockstep also implies keeping the input and ou ...
(DLL or PLL) circuits are recommended.
In a similar way, offset errors (non-zero readouts at ''T'' = 0) can be removed.
For long time intervals, the error due to instabilities in the
reference clock (
jitter
In electronics and telecommunications, jitter is the deviation from true periodicity of a presumably periodic signal, often in relation to a reference clock signal. In clock recovery applications it is called timing jitter. Jitter is a signifi ...
) plays a major role. Thus clocks of superior quality are needed for such TDCs.
Furthermore, external noise sources can be eliminated in postprocessing by
robust estimation methods.
Configurations
TDCs are currently built as stand-alone measuring devices in physical experiments or as system components like PCI cards. They can be made up of either discrete or integrated circuits.
Circuit design changes with the purpose of the TDC, which can either be a very good solution for single-shot TDCs with long dead times or some trade-off between dead-time and resolution for multi-shot TDCs.
Delay generator

The time-to-digital converter measures the time between a start event and a stop event. There is also a digital-to-time converter or delay generator. The delay generator converts a number to a time delay. When the delay generator gets a start pulse at its input, then it outputs a stop pulse after the specified delay. The architectures for TDC and delay generators are similar. Both use counters for long, stable, delays. Both must consider the problem of clock quantization errors.
For example, the
Tektronix
Tektronix, Inc., historically widely known as Tek, is an American company best known for manufacturing test and measurement devices such as oscilloscopes, logic analyzers, and video and mobile test protocol equipment. Originally an independent c ...
7D11 Digital Delay uses a counter architecture. A digital delay may be set from 100 ns to 1 s in 100 ns increments. An analog circuit provides an additional fine delay of 0 to 100 ns. A 5 MHz reference clock drives a
phase-locked loop
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is fixed relative to the phase of an input signal. Keeping the input and output phase in lockstep also implies keeping the input and ou ...
to produce a stable 500 MHz clock. It is this fast clock that is gated by the (fine-delayed) start event and determines the main quantization error. The fast clock is divided down to 10 MHz and fed to main counter. The instrument quantization error depends primarily on the 500 MHz clock (2 ns steps), but other errors also enter; the instrument is specified to have 2.2 ns of
jitter
In electronics and telecommunications, jitter is the deviation from true periodicity of a presumably periodic signal, often in relation to a reference clock signal. In clock recovery applications it is called timing jitter. Jitter is a signifi ...
. The recycle time is 575 ns.
Just as a TDC may use interpolation to get finer than one clock period resolution, a delay generator may use similar techniques. The
Hewlett-Packard
The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company. It was founded by Bill Hewlett and David Packard in 1939 in a one-car garage in Palo Alto, California ...
5359A High Resolution Time Synthesizer provides delays of 0 to 160 ms, has an accuracy of 1 ns, and achieves a typical jitter of 100 ps.
The design uses a triggered phase-locked oscillator that runs at 200 MHz. Interpolation is done with a ramp, an 8-bit digital-to-analog converter, and a comparator. The resolution is about 45 ps.
When the start pulse is received, then
count
Count (feminine: countess) is a historical title of nobility in certain European countries, varying in relative status, generally of middling rank in the hierarchy of nobility. Pine, L. G. ''Titles: How the King Became His Majesty''. New York: ...
s down and outputs a stop pulse. For low
jitter
In electronics and telecommunications, jitter is the deviation from true periodicity of a presumably periodic signal, often in relation to a reference clock signal. In clock recovery applications it is called timing jitter. Jitter is a signifi ...
the
synchronous counter has to feed a
zero flag from the
most significant bit
In computing, bit numbering is the convention used to identify the bit positions in a binary numeral system, binary number.
Bit significance and indexing
In computing, the least significant bit (LSb) is the bit position in a Binary numeral sy ...
down to the
least significant bit
In computing, bit numbering is the convention used to identify the bit positions in a binary number.
Bit significance and indexing
In computing, the least significant bit (LSb) is the bit position in a binary integer representing the lowes ...
and then combine it with the output from the Johnson counter.
A
digital-to-analog converter
In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function.
DACs are commonly used in musi ...
(DAC) could be used to achieve sub-cycle resolution, but it is easier to either use vernier Johnson counters or traveling-wave Johnson counters.
The delay generator can be used for
pulse-width modulation
Pulse-width modulation (PWM), also known as pulse-duration modulation (PDM) or pulse-length modulation (PLM), is any method of representing a signal as a rectangular wave with a varying duty cycle (and for some methods also a varying peri ...
, e.g. to drive a
MOSFET
upright=1.3, Two power MOSFETs in amperes">A in the ''on'' state, dissipating up to about 100 watt">W and controlling a load of over 2000 W. A matchstick is pictured for scale.
In electronics, the metal–oxide–semiconductor field- ...
to load a
Pockels cell within 8 ns with a specific charge.
The output of a delay generator can gate a digital-to-analog converter and so pulses of a variable height can be generated. This allows matching to low levels needed by analog electronics, higher levels for
ECL and even higher levels for
TTL. If a series of DACs is gated in sequence, variable pulse shapes can be generated to account for any transfer function.
See also
*
Sampling frequency
In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples".
A sample is a value of the signal at a point in time and/or s ...
, the average number of samples obtained per second
*
Multivibrator, electronic circuit used to implement simple two-state devices
*
Lidar
Lidar (, also LIDAR, an acronym of "light detection and ranging" or "laser imaging, detection, and ranging") is a method for determining ranging, ranges by targeting an object or a surface with a laser and measuring the time for the reflected li ...
, optical ranging technique
*
Time-of-flight, time something takes to travel a distance through a medium
References
External links
*
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*
* Università degli studi Roma Tre, Scuola Dottorale in Scienze Matematiche e Fisiche
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