Download Ben-Gurion University Faculty of Natural Sciences Department of Physics Undergraduate Project in Physics:

Ben-Gurion University
Faculty of Natural Sciences
Department of Physics
Undergraduate Project in Physics:
Precision measurements with alkali vapor cells
High frequency induction heating
Submitted by: Maxim Sokol
Advisor: Dr. David Groswasser
Content:
1. Abstract
2
2. Theoretical background - Vapor cells
3
2.1 Introduction - Vapor cells
2.2 Fine and hyperfine structure of the Rb atom
2.3 Alkali vapor cells
2.4 Interaction with radiation field and decoherence effects
3. Theoretical background – Induction heating
3.1 Introduction – Induction heating
3.2 Induction heating
3.2.1 How does induction heating works?
3.2.2 Practical implementation
4. System design
3
3
4
5
6
6
7
7
8
9
4.1 Power amplifier design
4.2 Work-coil design
4.3 Parallel resonant tank design
4.4 Heat transfer and heating time
9
10
13
15
5. Measurement, configuration and results
5.1 Equipment
5.2 Heat transfer and heating time
5.3 Results - heating time
15
15
17
18
6. References
19
7. APEX PA119CE/PA119CEA datasheet
20
1
1. Abstract
Precision measurements based on light interaction with alkali vapor are important in
various metrology fields (atomic clocks, magnetometers etc.). Often, the sensitivity
of these measurements is limited by decoherence time of the alkali atoms in the
vapor cell.
It was found that the two main decoherence mechanisms are atom-atom collisions
between alkali atoms and atom-wall collisions. The purpose of this project is to
reduce decoherence rate due to atom-wall collision by paraffin coating of the inner
vapor cell’s walls.
The preparation process of such paraffin coated vapor cells is complex and is carried
out only by a limited number of skilled experts in the world. The AtomChip group
initiated a program to develop such a process in our university.
A part of the vapor cell production process is to depose the paraffin on the cell walls.
Paraffin at room temperature is solid. In order to deposit a homogenous layer it has
to be heated and evaporated on the cell walls. However, the cell is evacuated so that
the heat transfer from outside the cell to the paraffin sample is problematic. We
decided to solve this problem by using induction heating (Induction heating is the
process of heating an electrically conducting object, usually a metal by
electromagnetic induction).
Our task in this project is to characterize, design and build a small induction heating
system that will be used in the vapor cell filling facility build by the AtomChip group.
(1)
(2)
(3)
Figure 1. 1:
Vapor-cell filling system, including the turbo pump (1), buffer gas
2 in fig. 4.2.1. & fig. 4.2.2.
manifold (2) and glass manifold (3) see detailed view
2. Theoretical background - Vapor cells
2.1. Introduction - Vapor cells
Alkali atoms are ideal systems for precision measurements. They have a single
electron at the outer shells (S). This electronic structure is very convenient for
calculations of the atomic spectrum and transitions. In addition, their ground state is
split into two sub-states with very ultra-narrow natural spectral width. The energy
difference between these two sub-levels (typically refers to as the “hyperfine split”)
corresponds to frequencies in the microwave range. As the lifetime of these levels is
ridiculously long, the natural width of these sub-levels is very narrow. Therefore, the
hyperfine transition frequencies can be used as highly accurate frequency standards.
In fact, these standards are so accurate that one of them is used to define the
second:
The natural frequency of the hyperfine split in 133Cs defines the SI second: The
second is the duration of 9,192,631,770 periods of the radiation at a frequency
corresponding to the transition between the two hyperfine levels of the ground state
of the 133Cs atom. Another alkali element that is typically used as a frequency
standard is 87Rb, with a hyperfine split corresponding to 6,834,682.610.90429Hz.
2.2. Fine and hyperfine structure of the Rb atom
Rubidium – Rb, is an alkali metal in atom configuration of [Kr]5S1, existing typically in
nature as 72% 85Rb and 28% 87Rb. 87Rb atom has a fine structure of J (electron total
angular momentum) equals to 1/2 in it ground state. By interacting an atom with
laser of wavelength ~780nm, an electron can be excited from 5S1/2 to 5P1/2 (D2
transition), or by interaction with
laser of wavelength ~795nm it might
be excited to 5P3/2 (D1 transition).
Those energy splits are a result of an
interaction between the electron spin
and the electrons' orbital angular
momentum, often called the Fine
split. The hyperfine structure occurs
due to the interaction of the nuclear
magnetic dipole moment in the
magnetic field generated by the
electrons, and the interaction of the
nuclear electric quadruple moment in
the electric field gradient due to the
Figure 2.2.1:
87
Rb fine and hyperfine split diagram
distribution of charge with the
atom.
3
2.3. Alkali vapor cells
The Technology of vapor
cell manufacturing already
exists for several decades.
Such cells are typically
made of an evacuated
tube made of optical
quality glass with a drop of
alkali metal inside. From
basic
thermodynamic
equations
the
vaporpressure of the alkali metal
inside the cell can be
calculated as function of
the cell temperature. In
practice, in cells that are
produced by the AtomChip
group the Rb vapor
pressure is deliberately
kept bellow the solid-vapor
equilibrium value.
Figure 2.3.1:
Vapor pressure of 87Rb.
For many years alkali vapor cells comprising Lithium (Li), Sodium (Na), Potassium (K),
Rubidium (Rb), Cesium (Cs), and Francium (Fr) are used as atomic references in
spectroscopy. Cs and Rb are also commonly used in atomic clocks as frequency
standards. In recent years there is a growing interest in Na, K, Rb and Cs cells also for
optical magnetometery measurements. Optical magnetic sensors based on alkali
vapor are the most sensitive probes of magnetic fields reaching extreme sensitivities
of sub fT/Hz1/2!
4
2.4. Interaction with radiation field and the decoherence effect
The accuracy of any measurement based atom-light interaction is dependent on the
coherence time of the atomic ensemble. If the phase evolution in the sample is not
homogenous, each atom will obtain a different phase,
and during the measurement will give a different signal.
As a result, the overall output signal will be “garbles”, or
even averaged out to zero. In vapor cells, the leading
decoherence processes that are responsible for loss of
phase between the atoms are collisions between alkali
atoms and collisions of alkali atoms with the glass walls
of the cell. It was found that decoherence due to
collisions between alkali atoms may be significantly
reduced by adding inert buffer gasses such as He, Ar, Xe
or N2 to the cell. Under such condition the collision
frequency between alkali atoms is significantly reduced
while collisions with the buffer gas do not change the
Figure 2.4.1:
spin state of the alkali atom. In addition, it was found
Rubidium vapor cell.
that when coating the glass walls with a thin layer of
paraffin or a similar derivative, the coherence time is increased by more the a factor
1000. This is since alkali-paraffin collisions are "spin-preserving" and do not affect
the phase evolution of the alkali atom. However, the coating process of vapor cells
with paraffin is long and tricky. As a result, the production yield is very low and only
a handful of research groups worldwide apply it. Obviously, the problem of collisions
with the cell walls is increased in miniaturized vapor cells. Thus, there is an
increasing motivation for developing a reliable paraffin coating procedure.
5
3. Theoretical background – Induction heating
3.1. Introduction – Induction heating
Induction heating is a non-contact heating process. It uses high power AC fields to
resonantly heat materials that are electrically conductive. Since it is non-contact, the
heating process does not contaminate the material being heated. It is also very
efficient since the heat is actually generated inside the workpiece. For these reasons
induction heating lends itself to some unique applications in industry, for example:
heating electrically conductive material in a clean, efficient and controlled manner.
As we describe in section 1 and section 2.3, devices based on rubidium vapor cells
are very sensitive to atom-wall interactions which can shift the rubidium hyperfine
transition frequency and even depolarize the atoms (decoherence).
Previous studies have shown that long polarization times may be achieved by coating
the inner surface of the vapor cell which containing the rubidium with a "separating
material". Also studies have shown that in cell with tetracontane - C40H82
(component of standard paraffin) coated inner walls, 87Rb atom can bounces even
105 times from the surface without losing its polarization as shown in figure 3.1.1.
The tetracontane coating process is very complicated. The tetracontane is
evaporated to homogenously coat the walls, but this must happen under vacuum
and that's why an induction heating system is required.
Figure 3.1.1:
Zeeman resonances at B=0.28 gauss from
uncoated and tetracontane coated Pyrex cells.
6
3.2. Induction heating
3.2.1. How does induction heating works?
A source of high frequency electric field is used to drive a large alternating current
through the work-coil. The current flow through the work-coil generates a very
intense and rapidly changing magnetic field in the space within the work-coil. The
workpiece to be heated is placed within this intense alternating magnetic field. The
alternating magnetic field induces a current flow in the conductive workpiece.
The arrangement of the work-coil and the workpiece can be thought of as an
electrical transformer (Figure 3.2.1.1). The work-coil is like the primary where
electrical energy is fed in, and the workpiece is like a single turn secondary that is
short-circuited.
Ideal transformer equation: (1)
Vs N s I p


Vp N p I s
This causes tremendous currents to flow through the
workpiece. Those currents are known as eddy
currents.
Figure 3.2.1.1:
The ideal transformer as a circuit
element.
Now, depending on the nature of the workpiece material, number of effects happen:
First, these eddy currents flow against the electrical resistivity of the metal,
generating localized heat. This heating occurs with both magnetic and non-magnetic
parts, and is often referred to as the "Joule effect", referring to Joule's first law:
(2) Q  I 2  R  t
Where Q is the amount of heat produced, I is the current flowing through the part
(workpiece), R is the electrical resistance of the part, and t = time.
Secondly, due to the high frequency used in induction heating applications gives rise
to a phenomenon called skin effect. This skin effect forces the alternating current to
flow in a thin layer towards the surface of the workpiece. The skin effect increases
the effective resistance of the metal to the passage of the large current. Therefore it
greatly increases the heating effect caused by the current induced in the workpiece.
(3)  
1
0


r  f
 503

r  f
Where δ is the skin depth, ρ it the resistivity of the medium, μr is the relative
permeability of the medium and f is the frequency of the wave.
7
Finally, additional heat is produced within magnetic parts through hysteresis - The
intense alternating magnetic field inside the work-coil repeatedly magnetizes and
de-magnetizes the iron crystals. This rapid flipping of the magnetic domains causes
considerable friction and heating inside the material. Heating due to this mechanism
is known as Hysteresis loss, and is greatest for materials that have a large area inside
their B-H curve. This can be a large contributing factor to the heat generated during
induction heating, but only takes place inside ferrous materials.
3.2.2. Practical implementation
The work-coil is usually connected to a resonant tank circuit. This has a number of
advantages. Firstly, it makes either the current or the voltage waveform become
sinusoidal. This minimizes losses in the amplifier circuit. The sinusoidal waveform at
the work-coil also represents a more pure signal and causes less RF (Radio
Frequency) interference to nearby equipment. We will see and discuss about two
main resonant schemes:
Series resonant tank circuit:
The work-coil is made to resonate at the intended operating frequency by means of
a capacitor placed in series with it. This causes the current through the work-coil to
be sinusoidal. The series resonance also magnifies the voltage across the work-coil,
far higher than the output voltage of the amplifier alone. The amplifier sees a
sinusoidal load current but it must carry the full current that flows in the work-coil.
These high currents make the design of the amplifier very complex.
Parallel resonant tank circuit:
The work-coil is made to resonate at the intended operating frequency by means of
a capacitor placed in parallel with it. This causes the current through the work-coil to
be sinusoidal. The parallel resonance also magnifies the current through the work
coil, far higher than the output current capability of the amplifier alone. The
amplifier sees a sinusoidal load current. However, in this case it only has to carry the
part of the load current that actually does real work. The amplifier does not have to
carry the full circulating current in the work-coil. Thus makes the design of the
amplifier
less
complex.
Figure 3.2.2.1:
From left to right - Series resonant tank
circuit, Parallel resonant tank circuit.
8
4. System design
4.1. Power amplifier design
One of our main demands was high and stable frequency BW (bandwidth), in order
not to limit ourselves in the resonant tank circuit design. The second issue was the
power output capability. In order to keep relatively high power outputs at high
frequencies a high slew-rate is a must.
By taking to consideration all the said below, workpiece dimensions, material nature
and the desired heating time. We came to decision to base the amplifier on the APEX
PA119CE/PA119CEA (datasheet is attached) power operational amplifier chip.
All the circuit design and all the frequencies simulations were performed by OrCAD
PSpice 10.5 and all the real-time simulations were performed by National
Instruments Circuit Design Suite 11.0.
Figure 4.1.1:
Power amplifier - main circuit.
ORcAD PSpice 10.5.
9
(1)
(2)
Figure 4.1.2:
(3)
4.2.
Workamplifier
coil design
Assembled
including the PCB (1), heatsink
(2) and fan (3).
During the work-coil design two
main demands were always in
front of us. The first was the coil
dimensions – the work-coil should
fit into the vacuum system (see fig.
4.2.2) as was described in sections
1 and section 2.4 (see fig. 4.2.1).
Second, in order to get high
currents, the reactive impedance
must to be low.
(4) X L  j L  L 
XL
j
Work-coil position
Figure 4.2.1:
A diagram of the glass manifolds used for cell
production and filling in the AtomChip lab.
When XL is the reactive impedance and L is the coil induction.
From equation (4) we can immediately see that a low inductance was needed.
10
Glass Manifold
Workpiece
Work-coil
Figure 4.2.2:
Work-coil and workpiece position on a prototype
glass manifold.
Work-coil dimensions:
r – radius of the coil
l – length of coil
N – numbers of turns
5mm
10cm
70
The inductance formula for a cylindrical coil is:
(5) L 
0 N 2 r 2
l
; 0  4  107 [
H
]
m
From equation (5) the coil inductance can be calculated:
4  107  2  702  (5  103 )2
L
 4.83 H .
0.1
From measurements that we performed, the "real" inductance is L  4.6 H .
11
Workpiece
Figure 4.2.3:
Work-coil ( L  4.6  H ) during a heat
process with workpiece inside.
Figure 4.2.4:
Workpiece (made of steel) model.
12
4.3. Parallel resonant tank design
As described in section 3.2.2, a parallel resonant tank was chosen.
On one hand, low reactive impedance and a deeper skin penetration are needed
(lower frequency – section 3.2.1) in order to get high currents. On the other hand,
we want also to get heat generation from the magnetic hysteresis effect (higher
frequency – section 3.2.1).
Using ORcAD PSpice 10.5 for frequency sweep simulations a 200-300 kHz range was
chosen.
Figure 4.3.1:
ORcAD PSpice frequency sweep
simulations circuit.
We chose capacitors with values suitable to this frequency range. Due to the fact
that temperature has a significant effect on capacitor parameters we decide to use
few capacitors in a serial/parallel mode in order to decrease heat generation and
increase heat dissipation.
X L  X C  2 f  L 
Resonant frequency calculation:
 f resonant 
13
1
2 LC
1
2 f  C
Graph 4.3.1:
Work coil voltage as a function of frequency.
V (in) =2v – without amplifier.
Graph 4.3.2:
Vout/Vin as a function of frequency.
V (in) =2v – without amplifier.
14
It's easy to see from graphs 4.3.1 and 4.3.2 that when the workpiece is inserted
inside the work coil there is a voltage drop on the work coil. This voltage drop can be
attributed to a power transfer from the work coil into the workpiece.
Another interesting note is that the workpiece slightly shifts the resonant frequency
and degrades the Q factor (graph 4.2.1). Therefore, the input frequency should be
adjusted in order to get maximum power after the workpiece has been positioned
inside the work coil.
5. Measurement, configuration and results
5.1. Equipment
As described in previous theoretical
section - in order to determine the
transmitted power we need to measure
the difference in the supplied current and
voltage over the work coil. The
measurement of this current was done by
the main power supply's internal current
meter.
Figure 5.1.1:
Main power supply's internal
current and voltage meter
In section 4.3 we saw from graph 4.3.1 that when the workpiece insert inside the
work coil there is a slightly shift in the resonant frequency. In order to determine
exactly the resonant frequency we used an oscilloscope – model Fluke 199c. This
oscilloscope model has a dual input with separated grounds. This feature made the
measurement process very convenient and gave as the possibility to simultaneously
measure the voltage over the work-coil and the amplifier output in parallel to keep
the amplifier steady as possible. Another oscilloscope – model Tektronix TDS210 was
used for measuring the input signal.
15
Figure 5.1.2:
Fluke 199c - oscilloscope
Figure 5.1.3:
Tektronix TDS210 - oscilloscope
The last measurement device used in this project is the temperature meter – model
Fluke 187. The temperature meter was attached directly to the workpiece with a
bimetal wire.
Figure 5.1.4:
Fluke 187 - temperature meter
Figure 5.1.5:
General view of the system - amplifier, resonant
tank, power supply, signal generator, two
oscilloscopes and the temperature meter.
16
5.2. Heat transfer and heating time
In order to calculate the energy needed for the heating procedure we can use the
next equation:
(6) E  m  T  Cp
E is the energy, m is the workpiece mass, T is the temperature and Cp is the specific
heat capacity.
When we find the energy needed in order to heat the workpiece we can calculate
the time needed for this procedure:
(7) T 
E
P
Where, P is the power.
The mass of the workpiece is about 15gr.
Average heat capacity for steels is 0.46 [kJ/Kg∙K].
Temperature that we would like to achieve is about 200 °C => ΔT=175 °C or °K.
 E  1220 J
By measuring the voltage and the difference in the current at the amplifier output,
we can calculate the power involved in the heating procedure:
(8) PNet  V  I  10 w
Now the time for the process can be calculated:
T
1220
 122sec  2.03min
10
This number is really close to the time measured (see section 6), that stands about
2.25min.
17
5.3. Results - heating time
As we describe in section 5.2 the heating time is proportional to the energy received
by the workpiece. Many repeated measurements were done (more than twenty) and
the results were steady and constant:
Graph 5.3.1:
Heating time of the workpiece as
a function of time.
As we can see from graph 5.3.1 there is a slightly curve shift. That curve shift occurs
due to high currents inside the work coil, and those currents heat the work coil.
Temperature has a strong influence on material properties like electric parameters,
which change the coil inductance and resistance.
When the coil temperature stabilizes at 120 °C the curve gets stable too.
In section 5.2 we semi-theoretically (the electrical power was measured) calculated
the heating time: Tcalc  2.03sec and from real measurements we get a very close
result: Tmesured  2.25sec .
18
6. References:
[1] – D. F. Phillips, A. Boca and R. L. Walsworth, "Evaporative Coating of Rb Maser
Cell", http://cfa-www.harvard.edu/~dphil/work/coat.pdf (1999).
[2] – D. A. Steck "Rubidium 87 D Line Data", revision 1.6. Source –
http://steck.us/alkalidata (2003).
[3] – S. Cartalevaa, T. Karaulanova, N. Petrova, D. Slavova, K. Vasevaa, A. Yaneva, M.
Mijailovicb, Z. Grujicb, "All-Optical Magnetometer Based on Resonant
Excitation of Rubidium Atoms by Frequency Modulated Diode Laser Light",
ACTA Phys. Pol. A 112, 871 (2007).
[4] – Bison G, Castagna N, Hofer A, et al, "A room temperature 19-channel magnetic
field mapping device for cardiac signals", Appl. Phys. Lett. 95, 173701 (2009).
[5] – Affolderbach, C., Stahler, M., Knappe, S. & Wynands, R., "An all-optical, high
sensitivity magnetic gradiometer", Appl. Phys. B 75, 605–612 (2002).
[6] – R. Michael Garvery, "Atomic Frequency Standards", ITSF 06 (2006)
[7] – M. Shuker, O. Firstenberg, R. Pugatch, A. Ron, and N. Davidson,
"Storing images in worm atomic vapor", Phys. Rev. Lett. 100, 223601 (2008).
[8] – M. Klein, I. Novikova, D.F. Phillips, and R.L. Walsworth, “Slow light in paraffincoated Rb vapor cells”, Journal of Modern Optics 53, 2583 (2006).
[9] – V. Rudnev, D. Loveless, R. Cook, M. Black, "Handbook of Induction Heating",
New York: Marcel Dekker (2003).
[10] – E.J.Davies, "Conduction and induction heating", IEE Power Engineering Series
II, Peter Peregrinus Ltd, (1990).
[11] – M. Fishenden, O.A. Saunders "An Introduction to Heat Transfer" Oxford
University Press. Oxford, (1950).
19
PA119CE
• PA119CEA
PA119CE
• PA119CEA
Product
IPnr no od vuac t i oI nn n o v a t i o n F r o m
PA119CE,
PA119CEA
From
Video Power Operational Amplifier
FEATURES
• VERY FAST SLEW RATE — 900 V/µs
• POWER MOS TECHNOLOGY — 4A peak rating
• LOW INTERNAL LOSSES — 0.75V at 2A
• PROTECTED OUTPUT STAGE — Thermal Shutoff
• WIDE SUPPLY RANGE — ±15V TO ±40V
APPLICATIONS
8-pin TO-3
PACKAGE STYLE CE
• VIDEO DISTRIBUTION AND AMPLIFICATION
• HIGH SPEED DEFLECTION CIRCUITS
• POWER TRANSDUCERS UP TO 5 MHz
• MODULATION OF RF POWER STAGES
• POWER LED OR LASER DIODE EXCITATION
TYPICAL APPLICATION
DESCRIPTION
The PA119 is a high voltage, high current operational amplifier optimized to drive a variety of loads from DC through the
video frequency range. Excellent input accuracy is achieved
with a dual monolithic FET input transistor which is cascoded
by two high voltage transistors to provide outstanding common
mode characteristics. All internal current and voltage levels
are referenced to a zener diode biased on by a current source.
As a result, the PA119 exhibits superior DC and AC stability
over a wide supply and temperature range.
High speed and freedom from second breakdown is assured
by a complementary power MOS output stage. For optimum
linearity, especially at low levels, the power MOS transistors
are biased in a class A/B mode. Thermal shutoff provides
full protection against overheating and limits the heatsink
requirements to dissipate the internal power losses under
normal operating conditions. A built-in current limit of 0.5A
can be increased with the addition of two external resistors.
Transient inductive load kickback protection is provided by
two internal clamping diodes. External phase compensation
allows the user maximum flexibility in obtaining the optimum
slew rate and gain bandwidth product at all gain settings. A
heatsink of proper rating is recommended.
This hybrid circuit utilizes thick film (cermet) resistors, ceramic
capacitors, and silicon semiconductor chips to maximize reliability, minimize size, and give top performance. Ultrasonically
bonded aluminum wires provide reliable interconnections at all
operating temperatures. The 8-pin TO-3 package is hermetically sealed and electrically isolated. The use of compressible thermal washers and/or improper mounting torque will
void the product warranty. Please see “General Operating
Considerations”.
TYPICAL
APPLICATION
+40V
±5mA
1K
DAC
110Ω
EQUIVALENT SCHEMATIC
3
Q1
Up to 4A
Q5
Q9
Q11
Q15
Q13
Q12
Q16
1
D1
Q19
Q20
5
Q17B
Q17A
Q21
4
Q22
Q23
Q24
7
Q25
D2
6
EXTERNAL CONNECTIONS
RCL+
+V
2
3
1
4
+IN
5.6pF
TOP
VIEW
5
–IN
8
6
–40V
PA119 AS FAST POWER DRIVER
www.cirrus.com
Q8
Q10
–V
PA119U
2
Q7
8
±32.5V
PA119
Q2
Q4
Q3
500Ω
RCL+
RCL–
This fast power driver utilizes the 900V/µs slew rate of the
PA119 and provides a unique interface with a current output
DAC. By using the DAC’s internal 1KΩ feedback resistor,
temperature drift errors are minimized, since the temperature
drift coefficients of the internal current source and the internal
feedback resistor of the DAC are closely matched. Gain of
VOUT to IIN is –6.5/mA. The DAC’s internal 1K resistor together
with the external 500Ω and 110Ω form a “tee network” in the
feedback path around the PA119. This effective resistance
equals 6.5KΩ . Therefore the entire circuit can be modeled
as 6.5KΩ feedback resistor from output to inverting input and
a 5mA current source into the inverting input of the PA119.
Now we see the familiar current to voltage conversion for a
DAC where VOUT = –IIN x RFEEDBACK.
Copyright © Cirrus Logic, Inc. 2010
(All Rights Reserved)
PHASE COMPENSATION
OUT
GAIN
CC
CC
1
10
100
1000
330pF
22pF
2.2pF
none
7
RCL–
FEB 20101
APEX − PA119UREVC
PA119CE • PA119CEA
ABSOLUTE MAXIMUM RATINGS
Product Innovation From
SUPPLY VOLTAGE, +VS to –VS
OUTPUT CURRENT, within SOA
POWER DISSIPATION, internal
INPUT VOLTAGE, differential
INPUT VOLTAGE, common mode
TEMPERATURE, pin solder — 10 sec
TEMPERATURE, junction1
TEMPERATURE, storage
OPERATING TEMPERATURE RANGE, case
SPECIFICATIONS
PARAMETER
TEST CONDITIONS 2
INPUT
OFFSET VOLTAGE, initial
OFFSET VOLTAGE, vs. temperature
OFFSET VOLTAGE, vs. supply
OFFSET VOLTAGE, vs. power
BIAS CURRENT, initial
BIAS CURRENT, vs. supply
OFFSET CURRENT, initial
INPUT IMPEDANCE, DC
INPUT CAPACITANCE
COMMON MODE VOLTAGE RANGE3
COMMON MODE REJECTION, DC
TC = 25°C
TC = 25°C to +85°C
TC = 25°C
TC = 25°C to +85°C
TC = 25°C
TC = 25°C
TC = 25°C
TC = 25°C
TC = 25°C
TC = 25°C to +85°C
TC = 25°C to +85°C, VCM = ±20V
GAIN
OPEN LOOP GAIN at 10Hz
OPEN LOOP GAIN at 10Hz
GAIN BANDWIDTH PRODUCT at 1MHz
POWER BANDWIDTH, AV = 100
POWER BANDWIDTH, AV = 1
TC = 25°C, RL = 1KΩ
TC = 25°C, RL = 15Ω
TC = 25°C, CC = 2.2pF
TC = 25°C, CC = 2.2pF
TC = 25°C, CC = 330pF
OUTPUT
VOLTAGE SWING3
VOLTAGE SWING3
VOLTAGE SWING3
SETTLING TIME to .1%
SETTLING TIME to .01%
SLEW RATE, AV = 100
SLEW RATE, AV = 10
TC = 25°C, IO = 4A
TC = 25°C to +85°C, IO = 2A
TC = 25°C to +85°C, IO = 78mA
TC = 25°C, 2V step
TC = 25°C, 2V step
TC = 25°C, CC = 2.2pF
TC = 25°C, CC = 22pF
POWER SUPPLY
VOLTAGE
CURRENT, quiescent
TC = 25°C to +85°C
TC = 25°C
THERMAL
RESISTANCE, AC, junction to case4
RESISTANCE, DC, junction to case
RESISTANCE, junction to air
TEMPERATURE RANGE, case
TC = 25°C to +85°C, F > 60Hz
TC = 25°C to +85°C, F < 60Hz
TC = 25°C to +85°C
Meets full range specifications
NOTES: *
1.
2.
3.
4.
CAUTION
2
MIN
PA119
TYP
±.5
10
10
20
10
.01
5
1011
6
±VS–15 ±VS–12
70
104
74
111
88
100
3.5
250
±VS–5 ±VS–1.5
±VS–3 ±VS–.75
±VS–1 ±VS–.5
.3
1.2
600
900
650
±15
–25
80V
5A
75W
40V
±VS
300°C
175°C
–65 to 150°C
–55 to 125°C
PA119A
MAX
MIN TYP
MAX
UNITS
±.35
±.75
5
15
*
*
5
50
*
3
25
*
*
*
*
mV
µV/°C
µV/V
µV/W
pA
pA/V
pA
MΩ
pF
V
dB
*
*
*
*
*
*
dB
dB
MHz
MHz
kHz
*
*
*
750
*
*
*
*
*
*
*
V
V
V
µs
µs
V/µs
V/µs
*
*
V
mA
±3
30
200
100
*
*
±35
100
±40
*
120
*
*
1.46
1.84
30
1.64
*
*
2.0
*
*
*
+85
*
*
°C/W
°C/W
°C/W
°C
The specification of PA119A is identical to the specification for PA119 in applicable column to the left.
Long term operation at the maximum junction temperature will result in reduced product life. Derate internal power dissipation
to achieve high MTTF.
The power supply voltage for all specifications is the TYP rating unless noted as a test condition.
+VS and –VS denote the positive and negative supply rail respectively. Total VS is measured from +VS to –VS.
Rating applies if the output current alternates between both output transistors at a rate faster than 60Hz.
The internal substrate contains beryllia (BeO). Do not break the seal. If accidentally broken, do not crush, machine, or
subject to temperatures in excess of 850°C to avoid generating toxic fumes.
PA119U
PA119CE • PA119CEA
POWER DERATING
70
CURRENT LIMIT, ILIM (A)
CL
20
10
0
0
200
OUTPUT VOLTAGE, VO (V)
SLEW RATE, (V/s)
400
100
80
60
40
10M 100M
10K 100K
1M
FREQUENCY, F (Hz)
POWER SUPPLY REJECTION, PSR (dB)
COMMOM MODE REJECTION, CMR (dB)
COMMON MODE REJECTION
120
PA119U
0
–30
–50 0
2
4 6 10 20 40 60 100 200 400
COMPENSATION CAPACITOR, CC (pF)
1K
10
–20
40
20
VIN = 2V
AV = 10
tr = 10ns
RL = 15W
20
–10
100
80
21
15
11
| +VS | + | –VS | = 80V
8
100K 200K 600K1M 2M 4M 8M
FREQUENCY, F (Hz)
50 100 150 200 250 300
TIME, t (ns)
POWER SUPPLY REJECTION
100
80
60
40
20
0
1K
10K 100K 1M
10M 100M
FREQUENCY, F (Hz)
20M
INPUT NOISE
PULSE RESPONSE
30
RL = 15W
5
30
F
SLEW RATE VS. COMP.
1000
800
600
1
2
3
4
OUTPUT CURRENT, IO (A)
RL = 15W
41
2pF
–V
58
.2p
1.0
0
POWER RESPONSE
80
+V
0.5
30
40
50
60
70
80
TOTAL SUPPLY VOLTAGE, VS (V)
=2
100 1K 10K 100K 1M 10M 100M
FREQUENCY, F (Hz)
.6
=2
0
OUTPUT VOLTAGE SWING
.8
CC
F
RCL = ∞
.5
0pF
0p
F
1.0
1.0
= 33
33
20
2p
pF
RCL =
1.2W
1.2
CC
40
2.
22
1.5
1.4
CC
60
2.0
1.5
VOLTAGE DROP FROM SUPPLY (V)
80
.27
W
0
–50 –25 0 25 50 75 100 125
CASE TEMPERATURE, TC (C)
25
50
75 100 125 150
CASE TEMPERATURE, TC (C)
SMALL SIGNAL RESPONSE
100
2.5
OUTPUT VOLTAGE, VO (VPP )
30
=0
QUIESCENT CURRENT
1.6
INPUT NOISE VOLTAGE, VN (nV/ √ Hz)
50
40
OPEN LOOP GAIN, AOL (dB)
R
3.0
60
–20
CURRENT LIMIT
3.5
30
COMMON MODE VOLTAGE, VCM (VP–P)
INTERNAL POWER DISSIPATION, P(W)
80
NORMALIZED QUIESCENT CURRENT, IQ (X)
Product Innovation From
70
20
15
10
7
5
3
10
1K
100
10K 100K
FREQUENCY, F (Hz)
1M
COMMON MODE VOLTAGE
65
60
55
50
45
40
10
100 1K 10K 100K 1M 10M
FREQUENCY, F (Hz)
3
PA119CE • PA119CEA
Product Innovation From
GENERAL
Please read Application Note 1 "General Operating Considerations" which covers stability, supplies, heat sinking,
mounting, current limit, SOA interpretation, and specification
interpretation. Visit www.Cirrus.com for design tools that help
automate tasks such as calculations for stability, internal power
dissipation, current limit; heat sink selection; Apex Precision
Power’s complete Application Notes library; Technical Seminar
Workbook; and Evaluation Kits.
CURRENT LIMIT
Q2 (and Q25) limit output current by turning on and removing gate drive when voltage on pin 2 (pin 7) exceeds .65V differential from the positive (negative) supply rail. With internal
resistors equal to 1.2Ω, current limits are approximately 0.5A
with no external current limit resistors. With the addition of
external resistors current limit will be:
ILIM = .65V
RCL
+.54A
To determine values of external current limit resistors:
RCL =
.65V
ICL – .54A
PHASE COMPENSATION
At low gain settings, an external compensation capacitor is
required to insure stability. In addition to the resistive feedback
network, roll off or integrating capacitors must also be considered when determining gain settings. The capacitance values
listed in the external connection diagram, along with good
high frequency layout practice, will insure stability. Interpolate
values for intermediate gain settings.
1. The current handling capability of the MOSFET geometry
and the wire bonds.
2. The junction temperature of the output MOSFETs.
The SOA curves combine the effect of these limits and allow
for internal thermal delays. For a given application, the direction and magnitude of the output current should be calculated
or measured and checked against the SOA curves. This is
simple for resistive loads but more complex for reactive and
EMF generating loads. The following guidelines may save
extensive analytical efforts:
1. Capacitive and inductive loads up to the following maximums
are safe:
CAPACITIVE LOAD
±VS
40V .1µF
11mH
30V 500µF
24mH
20V 2500µF
75mH
15V ∞
100mH
2. Safe short circuit combinations of voltage and current are
limited to a power level of 100W.
3. The output stage is protected against transient flyback.
However, for protection against sustained, high energy
flyback, external fast-recovery diodes should be used.
SUPPLY CURRENT
The PA119 features a class A/B driver stage to charge and
discharge gate capacitance of Q7 and Q19. As these currents
approach 0.5A, the savings of quiescent current over that of a
class A driver stage is considerable. However, supply current
drawn by the PA119, even with no load, varies with slew rate
of the output signal as shown below.
SAFE OPERATING AREA (SOA)
SOA
10
5
4
3
ST
DY
t=
30
s
s
ST
AT
TC=25°C
E
10
20
30
40 50
80 100
INTERNAL VOLTAGE DROP SUPPLY TO OUTPUT, VS-VO (V)
4
SUPPLY CURRENT
VOUT = 60VP-P SINE
RL = 500 Ω
300
200
100
0
30K
10
0m
0m
EA
2
1
t=
400
SUPPLY CURRENT, IS (mA)
OUTPUT CURRENT FROM +VS or -VS
The MOSFET output stage of this power operational amplifier has two distinct limitations:
INDUCTIVE LOAD
100K 300K
1M
3M
FREQUENCY, F (Hz)
10M
OUTPUT LEADS
Keep the output leads as short as possible. In the video
frequency range, even a few inches of wire have significant
inductances, raising the interconnection impedance and limiting the output current slew rate. Furthermore, the skin effect
increases the resistance of heavy wires at high frequencies.
Multistrand Litz Wire is recommended to carry large video
currents with low losses.
PA119U
PA119CE • PA119CEA
Product Innovation From
THERMAL SHUTDOWN
STABILITY
The thermal protection circuit shuts off the amplifier when
the substrate temperature exceeds approximately 150°C. This
allows the heatsink selection to be based on normal operating
conditions while protecting the amplifier against excessive
junction temperature during temporary fault conditions.
Thermal protection is a fairly slow-acting circuit and therefore
does not protect the amplifier against transient SOA violations
(areas outside of the steady state boundary). It is designed to
protect against short-term fault conditions that result in high
power dissipation within the amplifier. If the conditions that
cause thermal shutdown are not removed, the amplifier will
oscillate in and out of shutdown. This will result in high peak
power stresses, destroy signal integrity, and reduce the reliability of the device.
Due to its large bandwidth, the PA119 is more likely to
oscillate than lower bandwidth power operational amplifiers.
To prevent oscillations a reasonable phrase margin must be
maintained by:
1. Selection of the proper phase compensation capacitor. Use
the values given in the table under external connections and
interpolate if necessary.The phase margin can be increased
by using a larger capacitor at the expense of slew rate.
Total physical length (pins of the PA119, capacitor leads
plus printed circuit traces) should be limited to a maximum
of 3.5 inches.
2. Keep the external sumpoint stray capacitance to ground
at a minimum and the sumpoint load resistance (input and
feedback resistors in parallel) below 500Ω. Larger sumpoint
load resistances can be used with increased phase compensation and/or by bypassing the feedback resistor.
3. Connect the case to any AC ground potential.
CONTACTING CIRRUS LOGIC SUPPORT
For all Apex Precision Power product questions and inquiries, call toll free 800-546-2739 in North America.
For inquiries via email, please contact [email protected].
International customers can also request support by contacting their local Cirrus Logic Sales Representative.
To find the one nearest to you, go to www.cirrus.com
IMPORTANT NOTICE
Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject
to change without notice and is provided "AS IS" without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant
information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale
supplied at the time of order acknowledgment, including those pertaining to warranty, indemnification, and limitation of liability. No responsibility is assumed by Cirrus
for the use of this information, including use of this information as the basis for manufacture or sale of any items, or for infringement of patents or other rights of third
parties. This document is the property of Cirrus and by furnishing this information, Cirrus grants no license, express or implied under any patents, mask work rights,
copyrights, trademarks, trade secrets or other intellectual property rights. Cirrus owns the copyrights associated with the information contained herein and gives consent for copies to be made of the information only for use within your organization with respect to Cirrus integrated circuits or other products of Cirrus. This consent
does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale.
CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL APPLICATIONS”). CIRRUS PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED TO BE
SUITABLE FOR USE IN PRODUCTS SURGICALLY IMPLANTED INTO THE BODY, AUTOMOTIVE SAFETY OR SECURITY DEVICES, LIFE SUPPORT PRODUCTS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF CIRRUS PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE FULLY AT THE CUSTOMER’S RISK AND CIRRUS DISCLAIMS AND MAKES NO WARRANTY, EXPRESS, STATUTORY OR IMPLIED, INCLUDING THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR PARTICULAR PURPOSE, WITH REGARD TO ANY CIRRUS PRODUCT THAT IS USED IN SUCH A MANNER. IF THE
CUSTOMER OR CUSTOMER’S CUSTOMER USES OR PERMITS THE USE OF CIRRUS PRODUCTS IN CRITICAL APPLICATIONS, CUSTOMER AGREES,
BY SUCH USE, TO FULLY INDEMNIFY CIRRUS, ITS OFFICERS, DIRECTORS, EMPLOYEES, DISTRIBUTORS AND OTHER AGENTS FROM ANY AND ALL
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Cirrus Logic, Cirrus, and the Cirrus Logic logo designs, Apex Precision Power, Apex and the Apex Precision Power logo designs are trademarks of Cirrus Logic, Inc.
All other brand and product names in this document may be trademarks or service marks of their respective owners.
PA119U
5