Analog electronics general introduction
This presentation is the property of its rightful owner.
Sponsored Links
1 / 33

Analog electronics – general introduction PowerPoint PPT Presentation


  • 72 Views
  • Uploaded on
  • Presentation posted in: General

Analog electronics – general introduction. Analog – continuous in time Digital – discrete in time Design of amplifiers and filters ADCs Logic gates Receivers, transmitters Storage cells. L. 001 010 100. Sensor. Filter. ADC. DSP. Amplifier. E. S. 1. 1. 0. 1. 0.

Download Presentation

Analog electronics – general introduction

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Analog electronics general introduction

Analog electronics – general introduction

  • Analog – continuous in time

  • Digital – discrete in time

  • Design of amplifiers and filters

  • ADCs

  • Logic gates

  • Receivers, transmitters

  • Storage cells

L

001

010

100

Sensor

Filter

ADC

DSP

Amplifier

E

S

1

1

0

1

0

Advanced analog circuit design


Analog electronics general introduction1

Analog electronics – general introduction

  • Digital design: compromise between power consumption and processing speed

  • Analog design: compromise between speed, power consumption, resolution, supply voltage, linearity…

  • Analog circuit are crosstalk and noise sensitive

  • Analog design can‘t be automatized

  • Different levels of abstraction

G

S

D

B

PMOS

A

Transistor

Verstärker

System

Advanced analog circuit design


Analog electronics in scientific applications

Analog electronics in scientific applications

  • Particle detectors with high spatial resolution

    • Semiconductor detectors with spatial resolution are today widely used in consumer digital cameras, professional HDTV cameras, medical imaging and in science-grade instruments for particle physics, astronomy, material and biology studies (x-ray diffraction imaging, electron-microscopy) and many other fields.

    • Spatial resolution of semiconductor detectors is achieved by segmenting the sensor surface into many small picture elements ("pixels"). Every segment has its own signal collecting region that can be readout individually.

    • These detectors are distinguishable from the sensors for consumer electronics either by its low noise and single-particle detection capability or by other properties such as 100% fill-factor, high time resolution, high dynamic range, radiation tolerance, etc.

  • Multi-channel systems

  • Pixel electronics

  • Signal amplification, signal transmission, sampling, comparison, A/D conversion, time-measurements, amplitude measurement

  • Amplifiers, filters, switched-voltage/current circuits, comparators, A/D convertors, oscillators…

  • AC analysis, feedback

  • Transistor models

  • Noise, threshold dispersion

  • Semiconductors – solid state physics

Advanced analog circuit design


Pixel electronics

Pixel electronics

Amplifier

P-”guard-ring”

N-well

Filter

Comparator

SRAM

Hit memory

DAC

55 μm

Advanced analog circuit design


Pixel sensors for particle physics

Pixel sensors for particle physics

  • Pixel sensors are used to detect high-energy charged particles, and to determine particle trajectories.

  • Since particles tracking requires many layers of planar detectors, tracking sensors should be as transparent for particles as possible. They should be very thin, otherwise the particles will be deflected from their initial trajectories.

  • Silicon is the best material for such detectors since silicon-based technologies offer the possibility to implement any possible semiconductor device (from PN junction to the completed signal processing electronics) on the sensor.

Advanced analog circuit design


Pixel sensors for particle physics1

Pixel sensors for particle physics

Advanced analog circuit design


Pixel sensors for particle physics2

Pixel sensors for particle physics

Advanced analog circuit design


Pixel sensors for medical imaging

Pixel-sensors for medical imaging

  • In the case of high energy photon (x-ray or gamma) detection for medical imaging, the requirements are opposite. Photon sensors should be thick enough to absorb the largest part of the radiation. Due to its low absorption coefficient, silicon is not the best material for high-energy photon detection.

  • The most of practical pixel sensors for such radiation are based on indirect detection. Such sensors consist of a layer of scintillator material that converts the high-energy photons into visible light. The light detection is then performed by a silicon pixel sensor layer.

Advanced analog circuit design


Pixel sensors for medical imaging1

Pixel-sensors for medical imaging

Advanced analog circuit design


Classification of pixel sensors

Classification of pixel-sensors

  • Hybrid- and monolithic detectors

    • Monolithic pixel detectors: An n x m pixel matrix is placed on one chip and usually connected by means of signal multiplexing to n (or less) readout channels placed on the same or different chip. Pixels of a monolithic detector must be equipped with a certain readout electronics that at least perform the simplest tasks such as signal clearing, multiplexing and in most cases the amplification. (Some of monolithic detectors employ even more complex in-pixel signal- processing and data reduction. In this case we are talking about "intelligent" pixels that can e.g. detect particle hits, perform A/D conversion, transmit pixel addresses, perform time measurements, etc.) There are n or less connections between the pixel matrix and the block of readout channels.

    • Hybrid pixel detectors: Each pixel on the sensor chip has its own channel on the readout chip. There are n x m connection between two chips.

  • Technology – custom or specific

    • The development of such detectors is relatively low-cost since they use modern commercially available and well characterized CMOS technologies.

    • Pixel detectors in the technologies that are specially developed or adjusted for particle (or visible light) detection, like the technologies on high resistance substrate, thick epi-layer, etc.

Advanced analog circuit design


Hybrid detectors with fully depleted sensors

Hybrid detectors with fully-depleted sensors

n-type collecting region

(n-diffusion)

Pixel i

Pixel i

Potential enegry (e-)

Signal collection

Substrate

P-type Si - depleted

P-type Si - depleted

P-type Si - undepleted

P-type Si - undepleted

Advanced analog circuit design


Hybrid detectors with fully depleted sensors1

Hybrid detectors with fully-depleted sensors

  • Standard (bump-bonded) hybrid pixel detectors

    • The bump-bonded hybrid pixel detectors are used in high-energy physics for particle tracking, and in medicine and synchrotron experiments as direct detectors for x-rays. They are based on a relatively simple pixel sensor (ohmic or with pn junctions) without any pixel electronics and bump-connections between the pixel sensor and the readout pixel chip

    • The connection between the sensor and the readout chip is mechanically complex and expensive, especially in the case of small pixel sizes.

Pixel

Readout chip

Min. pitch ~50 μm

Bumps

Fully-depleted sensor

Signal charge

Advanced analog circuit design


Analog electronics general introduction

Hybrid-detector for cell imaging

Power/signal supply for RO-chip

Bonding matrix for one RO-chip

Pixel matrix

RO-chip (in a “gel”-pack)

Advanced analog circuit design


Capacitive coupled hybrid detector

Capacitive coupled hybrid detector

Pixel

Readout chip

Glue

Smart diode- or fully-depleted sensor

Signal charge

Advanced analog circuit design


Capacitive coupled hybrid detector1

Capacitive coupled hybrid detector

Power supply

and cont. signals

for the readout chip

1.5 mm

Power supply

and cont. signals

for the sensor

Readout chip (CAPPIX)

Sensor chip (CAPSENSE)

Advanced analog circuit design


3d hybrid detector

3D hybrid-detector

  • 3D-integration is a technology that allows for both vertical and horizontal connection between electronic components placed on different chips (thinned dies) stacked vertically.

Pixel

Readout chip2

Wafer bond

TSV

Readout chip1

Wafer bond

Fully-depleted sensor

Signal charge

Advanced analog circuit design


Standard monolithic detector maps

Standard monolithic detector - MAPS

  • In the case of a standard monolithic CMOS sensor ("Monolithic Active Pixel Sensor“) - the sensitive area is undepleted epitaxially-grown silicon layer and the charge is spread and separated by diffusion. Some part of the charge is finally attracted by the next well/diffusion.

NMOS transistor in p-well

N-well (collecting region)

Pixel i

P-type epi-layer

P-type substrate

Energy (e-)

Charge collection (diffusion)

MAPS

Advanced analog circuit design


Standard monolithic detector maps1

Standard monolithic detector - MAPS

  • Pixel rows are consecutively "selected" by connecting their outputs (usually single-transistor amplifier outputs) to column lines. The pixel signals are in this way transported to the readout channels. Such a multiplexing requires at least one electronic switch per pixel implemented with a transistor.

Select(i)

Select(i+1)

Signal out

P-type epi-layer

P-type substrate

Advanced analog circuit design


Standard monolithic detector maps2

Standard monolithic detector - MAPS

  • MAPS are slower and not as radiation tolerant as the hybrid detectors.

  • standard MAPS do not allow implementation of complete set of CMOS electronics inside pixels (only n-channel FETs - NMOS transistors - can be used)

N-well (collecting region)

Pixel i

NMOS transistor in p-well

PMOS transistor in n-well

P-type epi-layer

P-type substrate

Energy (e-)

Signal loss

Signal collection

MAPS with a PMOS transistor in pixel

Advanced analog circuit design


Enhanced maps

Enhanced MAPS

Pixel

PMOS in a shallow p-well

NMOS shielded by a deep p-well

N-well (collecting region)

P-doped epi layer

INMAPS

Advanced analog circuit design


T well detector and smart diode array

T-well detector and smart diode array

P-well

Pixel

Deep n-well

2. n-well

NMOS

PMOS

Diffusion

Epi-layer

Pixel

T-well MAPS

Potential energy (e-)

“Smart” diode

Deep n-well

Drift

Potential energy (e-)

Depleted E-field region

P-substrate

“Smart diode” array

Advanced analog circuit design


Soi monolithic detector

SOI monolithic detector

  • An SOI detector is based on a modified SOI process. SOI detectors use the electronics layer for the readout circuits and the high-resistivity support layer as a fully-depleted (drift-based) sensor. The sensor is typically 300um thick and has the conventional form of a matrix of pn junctions. A connection through the buried oxide is made to connect the readout electronics with the sensor.

CMOS pixel electronics

Connection

Electronics layer

Buried oxide

Energy (e-)

Support layer

Advanced analog circuit design


Depfet monolithic detector

DEPFET monolithic detector

Pixel

PMOS

Ext. gate

Clear

Elect. Interact.

Int. gate

Int. gate

Signal clearing

Potential en. (e-)

Signal collection

N-substrate (depleted)

P-type backside contact

Advanced analog circuit design


Sdd monolithic detector

SDD monolithic detector

Drift “rings”

N-doped collecting region

Energy (e-)

Depleted n-type substrate

Undepleted p-type backside contact

Advanced analog circuit design


Monolithic detector sda

Monolithic detector - SDA

ADC channel

Pixel matrix

2.7 mm

Advanced analog circuit design


Amplification

Amplification

  • In its simplest form, pixel signal amplification is performed using a single-transistor amplifier. In the case of Field Effect Transistors (FETs), a single-transistor amplifier is sensitive to the voltage change on its input (gate). The charge signal generated by ionization is first collected by the collecting region. The amplifier is coupled with the collecting region by means of DC-coupling (wire) or by use of AC-coupling (capacitance). The conversion factor between the charge signal and the voltage change is the capacitance of the collecting region, referred to as detector capacitance. Clearly the voltage signal will be higher if the collection region has smaller capacitance.

  • More efficient amplification is achieved by multi-transistor amplifiers. Such amplifiers are typical for hybrid detectors and advanced CMOS monolithic detectors. They are often equipped with feedback circuit which makes the amplification more linear. An example of an amplifier with feedback is the charge sensitive amplifier - CSA. CSA is sensitive only to the charge injected into its input, the capacitance of the input node does not influence the output signal amplitude.

Advanced analog circuit design


Amplification1

Amplification

Bias V

Bias V

Charge sensitive amplifier

Bias R

Bias R

Out

Out

Isig

Isig

Cdet

Cdet

Simple voltage amplifier

(source follower)

Detector (equivalent circuit)

Detector

Advanced analog circuit design


Noise

Noise

  • An amplifier not only performs the amplification of the input signal; unfortunately it also introduces electronic noise. Let us explain this: Every amplifier needs to be biased in order to achieve the desired amplification, which means that the amplifier transistor(s) must conduct a certain bias- (DC) current. The signal on transistor's gate will then modulate the current. Thermal motion of the charge carriers inside the transistor active region (channel), leads to bias current fluctuations. These fluctuations are small compared to the bias current itself, but since the bias current is almost always much larger than the signal, its noise can in many cases exceed the signal. A way to decrease the noise is to extend the measurement time (or add a low-pass filter/shaper). Noise signals are random signals with expected value zero and if the measurement takes long time, the average of the noise during measurement interval will in fact approach zero. Most signals, however, have nonzero DC value and they are unaffected by the measurement time.

  • We could conclude that the detector capacitance does not play any role if we use CSA. This is, however, not true. The noise of a charge sensitive amplifier depends linearly on the detector capacitance. The reason for this is that the negative feedback which cancels the output noise becomes less efficient if the input amplifier node is loaded with a large capacitance.

Advanced analog circuit design


Noise1

Noise

Advanced analog circuit design


Time walk

„Time walk“

Advanced analog circuit design


Ktc noise

KTC Noise

  • Almost every electronic circuit that employs transistors will be affected by their noise. This holds also for the transistor-based pulsed-reset circuit. During the pulsed reset, i.e. when the reset switch is closed, the potential of the collecting region will fluctuate around the desired reset value due to the thermal noise in the reset transistor. When the reset transistor is turned off, the instantaneous value of the reset voltage will be frozen. The instantaneous value is the sum of the desired reset-voltage and the reset error. The reset error superposes to the signal and leads to a measurement uncertainty. It is interesting to note that the reset noise only depends on the detector capacitance (not on the reset transistor resistance):

  • σ2v = kT/Cdet,

  • with σ2v variance of the voltage reset error, k Boltzmann's constant, T temperature and Cdet detector capacitance.

Advanced analog circuit design


Ktc noise1

KTC Noise

Advanced analog circuit design


Properties of pixel sensors

Properties of pixel sensors

  • Properties

  • Pixel size

  • Detector capacitance

  • Noise

    • readout amplifier

    • reset- and bias-resistor noise

    • The leakage-current noise

    • σ2v = kT/(gm t).

    • The magnitude of the noise determines the smallest detectable signal.

  • Signal to noise ratio (SNR)

    • SNR is the ratio between a chosen reference signal and the noise.

    • SNR ~ (gm t)0.5/Cdet

  • Dynamic range

    • Dynamic range is the ratio between the greatest undistorted signal (the greatest signal for which the readout does not saturate) and the smallest detectable signal (determined by the noise).

  • Time resolution

  • Power consumption

    • FOM = P t / SNR2

  • Radiation tolerance

  • Fixed pattern noise

    • FPN refers to a non-temporal spatial noise and is due to device mismatch in the pixels and/or readout channels.

  • Radiation length

Advanced analog circuit design


  • Login