AUR (Z-Foil for Audio)
Vishay Foil Resistors
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Z-Foil Technology, Low Profile Conformally Coated for
Audio Applications with TCR Down to 0.05 ppm/°C,
Low Harmonic Distortion, and Noise Stabilization
FEATURES
• Temperature coefficient of resistance (TCR):
±0.05 ppm/°C nominal (0°C to +60°C)
±0.2 ppm/°C nominal (–55°C to +125°C, +25°C ref.)
(see Table 1)
• Tolerance: to ±0.01%
• Power rating: to 300 mW at +70°C
• Load life stability: to ±0.01% at 70°C, 2000 h at rated
power
• Resistance range: 5 Ω to 120 kΩ
• Vishay Foil resistors are not restricted to standard
values; specific “as required” values can be supplied at
no extra cost or delivery (e.g., 1K2345 vs. 1K)
• Significantly lower microphonics than any other resistor
technology
• Thermal stabilization time: <1 s (within 10 ppm of
steady state value)
• Electrostatic discharge (ESD): up to 25 kV
• Maximum working voltage: 300 V
• Non-inductive, non-capacitive design
• Rise time: 1 ns effectively no ringing
• Current noise of 0.010 μV
rms
/ V of applied voltage
(<–40 dB)
• Voltage coefficient <0.1 ppm/V
• Non-inductive: <0.08 μH
• Non hot spot design
• Terminal finish: lead (Pb)-free or tin/lead alloy
• Matched sets are available per request
AUR2
AUR2J
AUR
Hear the Difference
AURJ
They resign themselves to making constant adjustments
and troubleshooting. But in fact these can be avoided.
Instability is often traceable to a few supposedly “fixed”
resistors which are not really fixed at all. If these resistors
would only retain their original values, there would be
no need for costly controls and other compensating
circuitry. That’s why the only resistor for applications
such as these is Z Bulk Metal
®
Foil. In high-end audio
equipment, careful selection of resistors is one of the
best ways to avoid or minimize noise and distortion in the
signal path. Noise is an unwanted wide spectrum signal
that may be superimposed on any useful signal, including
DC. Resistors, like other passive components, are noise
sources to various degrees, depending upon resistance
value, temperature, applied voltage, and resistor type.
Many experiments have been done to show why some
resistors are “noisier” than others. But the only test
that audio experts and audiophiles have agreed on is
comparing the level of fidelity that results when different
resistor technologies are used in actual audio systems.
High-end analog audio applications require low intrinsic
noise, high linearity of amplification, and minimal dynamic
distortion. The typical audio amplifier consists of a voltage
preamplifier (preamp) and power amplifier (final driver).
The voltage preamplifier deals with low-level signals.
That is why its intrinsic noise level is critical. Resistors are
among the principal noise sources in the amplifiers. The
main requirements for the audio power amplifier are high
linearity of amplification and minimal dynamic distortion.
Vishay Foil resistors are characterized by very low intrinsic
non-linearity of the resistive element, which is made from
cold-rolled bulk metal.
The AUR, composed of VFR’s Bulk Metal
®
Z-foil
technology, with improved sound quality, provides
a combination of low noise and low inductance/
capacitance, making it unrivalled for applications requiring
low noise and distortion-free properties.
RELATED FACTS AT A GLANCE
Please refer to FACTS #106,
Selecting Resistors for Pre-
Amp, Amplifier, and Other High-End Audio Applications.
INTRODUCTION
Many manufacturers and users of precision electronic
equipment suffer needlessly from unexplained instabilities
and drifts due to noise effects and harmonic distortion.
Document No.: 63244
Revision: 02-Oct-2013
For questions, contact
foil@vishaypg.com
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1
AUR (Z-Foil for Audio)
Vishay Foil Resistors
FIGURE 1—STANDARD IMPRINTING AND DIMENSIONS
in Millimeters (Inches)
L
T
Resistance Value Code
Tolerance
Symbol
Date Code
13
45
Year Week
AUR
1345
H
10K0
T
Type
AUR
AURJ
L
5.8 ±0.5
(0.228 ±0.02)
H
5.5 ±1
(0.216 ±0.04)
T
2.2 ±0.5
(0.086 ±0.02)
LS
3.81 ±0.25
(0.150 ±0.01)
5.08 ±0.25
(0.200 ±0.01)
3.81 ±0.25
(0.150 ±0.01)
5.08 ±0.25
(0.200 ±0.01)
25.4
(1.0 min.)
LS
Lead Material #22 AWG (0.025 Diameter)
Solder Coated Copper
AUR2
AUR2J
6.7 ±0.5
(0.263 ±0.02)
8 ±1
(0.315 ±0.04)
2.78 ±0.5
(0.110 ±0.02)
Note
Letter J indicates a difference in lead spacing and -2 is an extension range.
Resistor
AUR2, AUR2J
Resistance
Value
(Ω)
60k to 120k
50 to <60k
Typical TCR and
Max. Spread
(ppm/°C)
±0.2 ±1.8
±0.2 ±1.8
±0.2 ±2.8
±0.2 ±4.8
±0.2 ±6.8
Tolerance
(%)
±0.02%
±0.01%
±0.02%
±0.02%
±0.05%
Percent of Rated Power
TABLE 1—TOLERANCE AND TCR VS.
RESISTANCE VALUE
(–55°C to +125°C, +25°C Ref.)
FIGURE 2—POWER DERATING CURVE
100
+ 70 °C
75
50
25
AUR, AURJ
20 to <50
10 to <20
5 to <10
0
- 75
- 50
- 25
0
+ 25
+ 50
+ 75 + 100 + 125 + 150 + 175
Ambient Temperature (°C)
TABLE 2—PERFORMANCE SPECIFICATIONS
Test
Moisture Resistance
Pressure Cooker Test
Short Time Overload
Resistance to Solder Heat
Terminal Strength
Insulation Resistance
Dielectric Withstanding Voltage
Thermal Shock
Shock
Vibration
Load Life Stability
Thermal EMF
Current Noise
Low Temperature Storage
Low Temperature Operation
High Temperature Exposure
Conditions
MIL-STD-202, method 106
2 atmospheres absolute pressure,
121°C, 100% R.H. for 100 h
6.25 x Pnom, 5 s
+260°C, 20 s
2 lbs, 10 s
DC 100 V, 2 min
AC 300 V, 1 min
–65°C to +150°C, 5 cycles
MIL-STD-202, method 213, condition I
MIL-STD-202, method 204, condition D
0.3 W, +70°C, 2000 h
—
Quan-Tech
24 h at –65°C
45 min at –65°C
+150°C
∆R (%), Typical
±0.005
±0.2
±0.005
±0.01
±0.0025
>10 000M
±0.0025
±0.01
±0.005
±0.01
±0.01
0.07 μV/°C
–40 dB
±0.005
±0.005
±0.01
∆R (%), Maximum
±0.03
±0.4
±0.05
±0.03
±0.03
>10 000M
±0.03
±0.02
±0.03
±0.03
0.015
0.1 μV/°C
–40 dB
±0.01
±0.01
±0.03
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Document No.: 63244
Revision: 02-Oct-2013
AUR (Z-Foil for Audio)
Vishay Foil Resistors
FIGURE 3—TRIMMING TO VALUES
(conceptual illustration)
Interloop
Capacitance
Reduction
in Series
Mutual Inductance
Reduction due
to Change in
Current Direction
Current Path
Before Trimming
Current Path After Trimming
Trimming Process
Removes this Material
from Shorting Strip Area
Changing Current Path
and Increasing
Resistance
Note
To acquire a precision resistance value,
the Bulk Metal
®
Foil chip is trimmed by
selectively removing built-in “shorting bars.”
To increase the resistance in known increments,
marked areas are cut, producing progressively
smaller increases in resistance. This method
reduces the effect of “hot spots” and improves
the long-term stability of the Vishay Foil resistors.
Foil shown in black, etched spaces in white
POST MANUFACTURING OPERATIONS
(PMO)
Many audio analog applications can include requirements
for performance under conditions of stress beyond the
normal and over extended periods of time. This calls for
more than just selecting a standard device and applying
it to a circuit. The standard device may turn out to be all
that is needed but an analysis of the projected service
conditions should be made and it may well dictate a
routine of stabilization known as post manufacturing
operations or PMO. The PMO operations that will be
discussed are only applicable to Bulk Metal Foil resistors.
They stabilize Bulk Metal Foil resistors while they are
harmful to other types. Short time overload, accelerated
load life, and temperature cycling are the three PMO
exercises that do the most to remove the anomalies down
the road. VFR Bulk Metal Foil resistors are inherently
stable as manufactured. These PMO exercises are only
of value on Bulk Metal Foil resistors and they improve the
performance by small but significant amounts. Users are
encouraged to contact Vishay Foil Resistors’ applications
engineering for assistance in choosing the PMO
operations that are right for their application.
be reduced by reducing resistance, temperature, or signal
bandwidth.
Shot or fluctuation noise is caused by the discrete nature
of charge carriers and fluctuation of their number in the
unit of volume. Shot noise can be reduced by reducing
bandwidth or increasing current. The spectral density
of voltage in both thermal and shot noises is uniformly
distributed in entire range of frequencies (“white” noise).
The level of these types of noise does not depend on
resistor type (resistive element material).
Current (excess, flicker) noise has 1/f type spectral
density of voltage (“pink” noise). Its level essentially
depends on resistor material. Current noise can be
reduced by (a) avoiding use of the low frequency band,
(b) reducing current, (c) increasing the volume of resistive
material, i.e. by using resistors with higher rated power
than is needed for proper power dissipation, or (d) using
less noisy resistive materials.
Carbon composition resistors are the noisiest such device
type followed by Thick Film and Thin Film resistors. The
least noisy are bulk metals and metal alloys (foil, wire). At
that, negligible capacitance/inductance of foil resistors
(when compared to wirewound resistors) significantly
reduces probability of self-excitation or “ringing” of
amplification circuit.This is why Bulk Metal
®
foil resistors
are such a good choice for low-noise applications.
SEVERAL TYPES OF NOISE
FOUND IN RESISTORS
Thermal noise is caused by thermal movement of
electrons in resistive material and gets worse as
resistance and temperature increase. Thermal noise can
Document No.: 63244
Revision: 02-Oct-2013
For questions, contact
foil@vishaypg.com
www.vishayfoilresistors.com
3
AUR (Z-Foil for Audio)
Vishay Foil Resistors
TABLE 4—GLOBAL PART NUMBER INFORMATION
(1)
NEW GLOBAL PART NUMBER: Y470012K7560T9L (preferred part number format)
DENOTES PRECISION
Y
VALUE
R
=Ω
K
= kΩ
CHARACTERISTICS
0
= standard
9
= lead (Pb)-free
1 to 999
= custom
Y
4
7
0
0
1
2
K
7
5
6
0
T
9
L
PRODUCT CODE
4700 =
AUR
4701 =
AURJ
4702 =
AUR2
4703 =
AUR2J
RESISTANCE TOLERANCE
T
= ±0.01%
Q
= ±0.02%
A
= ±0.05%
B
= ±0.10%
C
= ±0.25%
D
= ±0.5%
F
= ±1.0%
PACKAGING
L
= bulk
FOR EXAMPLE: ABOVE GLOBAL ORDER Y4700 12K7560 T 9 B:
TYPE: AUR
VALUES: 12.7560 kΩ
ABSOLUTE TOLERANCE: 0.01 %
TERMINATION: lead (Pb)-free
PACKAGING: bulk
HISTORICAL PART NUMBER: AUR T 12K756 T B (will continue to be used)
AUR
MODEL
AUR
AURJ
AUR2
AUR2J
T
TERMINATION
T
= lead (Pb)-free
None = tin/lead alloy
12K756
RESISTANCE
VALUE
12.756 kΩ
T
TOLERANCE
T
= ±0.01%
Q
= ±0.02%
A
= ±0.05%
B
= ±0.10%
C
= ±0.25%
D
= ±0.5%
F
= ±1.0%
B
PACKAGING
B
= bulk
Note
(1) For non-standard requests, please contact Application Engineering
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Document No.: 63244
Revision: 02-Oct-2013
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Vishay Precision Group, Inc.
Disclaimer
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not limited to, the warranty expressed therein.
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Copyright Vishay Precision Group, Inc., 2014. All rights reserved.
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Revision: 15-Jul-2014
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