VAR
Vishay Foil Resistors
Ultra High Precision, Z-Foil Audio Resistor Minimizes Noise and
Distortion in the Signal Path with TCR of ± 0.05 ppm/°C, Tolerance
to ± 0.005 % and High Linearity or Low Voltage Coefficient of
Resistance (VCR) of 0.1 ppm/V
FEATURES
Temperature coefficient of resistance (TCR):
± 0.05 ppm/°C typical (0 °C to + 60 °C,+ 25 °C
ref.) ± 0.2 ppm/°C typical (0 °C to + 125 °C,
+ 25 °C ref.)
Rated power: to 0.4 W at + 70 °C
Resistance tolerance: to ± 0.01 % (0.005% is available)
Load life stability: to ± 0.005 % at 70 °C, 2000 h at rated
power
Resistance range: 10
to
100 k
"Naked Z-foil resistor" design without molding or
encapsulation adds an additional dimension for reducing
signal distortion and increasing clarity in signal processing.
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)
Electrostatic discharge (ESD) at least to 25 000 V
Non-inductive, non-capacitive design
Rise time: 1 ns, effectively no ringing
Current noise: 0.010 µV (RMS)/Volt of Applied Voltage
(< - 40 dB)
Thermal EMF: 0.05 µV/°C
Voltage coefficient: < 0.1 ppm/V
Thermal stabilization time < 1 s (nominal value achieved
within 10 ppm of steady state value)
Inductance: < 0.08 µH typical
The Z-Foil chip in the VAR has been especially treated to
increase load life stability.
Terminal Finish: lead (Pb)-free or tin/lead alloy
(1)
Prototype quantities available in just 5 working days or
sooner. For more information, please contact
foil@vishaypg.com
For better performances please contact us.
INTRODUCTION
Many manufacturers and users of precision electronic
equipment suffer needlessly from unexplained instabilities
and drifts due to noise effects. 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 Vishay 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 VAR, composed of Vishay’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.
Document Number: 63140
Revision: 03-Jan-12
For any questions, contact:
foil@vishaypg.com
www.vishayfoilresistors.com
1
VAR
Vishay Foil Resistors
While the regular foil resistors are already widely
acknowledged as the leading resistors for audio applications,
the special “naked Z-foil resistor” design without mold or
encapsulation, adds an additional dimension for reducing
signal distortion and increasing clarity in signal processing.
Our application engineering department is available to
advise and to make recommendations. For non-standard
technical requirements and special applications, please
contact us.
Bulk Metal Foil resistors owe their low current noise and high
linearity to the type of material they’re made of: a several
microns thick cold-rolled metal foil. Every real-world resistor
possesses certain nonlinearity of its electrical resistance
(nonlinearity of volt-ampere characteristic). The degree of
nonlinearity depends on two factors:
Micro factors: internal microstructure of resistive material.
Macro factors (laser trimming cuts cleanness, micro
cracking in resistive element resulting from laser trimming,
quality of contacts between resistive element and
terminals, etc.).
As for the microstructure, the most linear materials are pure
metals and metal alloys in bulk, such as the foil in Bulk
Metal
®
Foil resistors. When the same materials are
deposited in the form of very Thin (nanometer range) Films,
they are less linear. Even less linear are composite materials
like resistive cermets in Thick-Film resistors or carbon
compositions in carbon composition resistors.
The macro factors that cause nonlinearity in other types of
resistors aren’t relevant to foil resistors. Indeed, laser
trimming of foil resistors consists of cutting shorting jumpers
and does not damage current carrying portions of resistive
element. Terminals in foil resistors are an integral part of the
foil resistive element. This insures high-quality contact
between resistive element and terminals
Several types of noise are 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 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.
FIGURE 1 - TYPICAL RESISTANCE /
TEMPERATURE CURVE
(Z-FOIL)
TCR chord slopes for different temperature ranges
+ 500
+ 400
+ 300
+ 200
+ 100
ΔR
0
R
(ppm)
- 100
- 200
- 300
- 400
- 500
- 55
- 25
0
+ 25
+ 60
+ 75
+ 100
+ 125
- 0.16 ppm/°C
0.05 ppm/°C
- 0.1 ppm/°C
0.1 ppm/°C
0.14 ppm/°C
0.2 ppm/°C
Ambient Temperature (°C)
TABLE 1 - RESISTANCE VERSUS TCR
(- 55 °C to + 125 °C, + 25 °C Ref.)
(2)
RESISTANCE VALUE
()
100 to < 100K
50 to < 100
10 to < 50
Note:
(1) Pb containing terminations are not RoHS compliant, exemptions may apply
(2) For non-standard requests, please contact application engineering at foil@vishaypg.com
www.vishayfoilresistors.com
2
For any questions, contact:
foil@vishaypg.com
Document Number: 63140
Revision: 03-Jan-12
TYPICAL TCR AND MAXIMUM SPREAD (ppm/°C)
± 0.2 ± 1.8
± 0.2 ± 2.8
± 0.2 ± 3.8
TIGHTEST TOLERANCE
(%)
0.01
0.01
0.02
VAR
Vishay Foil Resistors
FIGURE 2 - STANDARD DIMENSIONS
L
W
H
This product is fragile
and may be damaged
if mishandled.
VPG assumes no
responsibility for
damage caused by
improper handling.
LL
Soldered PCB
Lead Material #22 AWG
Round Solder Coated Copper
LS
TABLE 2 - SPECIFICATIONS
RESISTANCE RANGE
()
MAXIMUM
WORKING
VOLTAGE
AMBIENT
POWER RATING
at
+ 70 °C
at
+ 125 °C
INCHES
W: 0.080 max.
L: 0.250 max.
H: 0.310 max.
LL: 1.000 ± 0.125
LS
(1)
: 0.150 ±
0.005
DIMENSIONS
mm
W: 2.03 max.
L: 6.35 max.
H: 7.87 max.
LL: 25.4 ± 3.18
LS: 3.81 ± 0.13
10 to 100K
200
0.4 W
0.2 W
Note
1. An additional lead space option is available: 0.200" (5.08 mm). For these specifications - please specify VARJ (see Table 3) when placing
an order.
FIGURE 3 - POWER DERATING CURVE
200 %
- 55 °C
+ 70 °C
FIGURE 4 - TRIMMING TO VALUES
(Conceptual Illustration)
Percent of Rated Power at + 125 °C
Double Rated Power
175 %
150 %
125 %
100 %
75 %
50 %
25 %
0
- 75
Interloop Capacitance
Reduction in Series
Current Path
Before Trimming
Current Path
After Trimming
Trimming Process
Removes this Material
from Shorting Strip Area
Changing Current Path
and Increasing
Resistance
Rated Power
Mutual Inductance
Reduction due
to Opposing
Current in
Adjacent Lines
- 50
- 25
0
+ 25
+ 50
+ 75 + 100 + 125 + 150 + 175 + 200
Ambient Temperature (°C)
Note:
Foil shown in black, etched spaces in white
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 spot” and improves the long term stability of the hybrid
chips.
For any questions, contact:
foil@vishaypg.com
www.vishayfoilresistors.com
3
Document Number: 63140
Revision: 03-Jan-12
VAR
Vishay Foil Resistors
TABLE 3 - GLOBAL PART NUMBER INFORMATION
(1)
NEW GLOBAL PART NUMBER: Y070680K5000T9L (preferred part number format)
DENOTES PRECISION
RESISTOR
Y
VALUE
R
=
K
= k
Characteristics
0
= standard part, tin/lead termination
9
= standard part, lead (Pb)-free termination
1 - 999
= custom
Y
0
7
0
6
8
0
K
5
0
0
0
T
9
L
PRODUCT CODE
0706
= VAR
0707
= VARJ
RESISTANCE TOLERANCE
T
= ± 0.01 %
Q
= ± 0.02 %
A
= ± 0.05 %
B
= ± 0.1 %
C
= ± 0.25 %
D
= ± 0.5 %
F
= ± 1.0 %
PACKAGING
L
= bulk pack
FOR EXAMPLE: ABOVE GLOBAL ORDER Y0706 80K5000 T 9 L:
TYPE: VAR
VALUE: 80.5 k
ABSOLUTE TOLERANCE: ± 0.01 %
TERMINATION: lead (Pb)-free
PACKAGING: bulk pack
HISTORICAL PART NUMBER: VAR T 80K5 T B (will continue to be used)
VAR
MODEL
VAR
T
TERMINATION
T
= lead (Pb)-free
None = tin/lead alloy
80K5
RESISTANCE VALUE
80.5 k
T
TOLERANCE
T
= ± 0.01 %
Q
= ± 0.02 %
A
= ± 0.05 %
B
= ± 0.1 %
C
= ± 0.25 %
D
= ± 0.5 %
F
= ± 1.0 %
B
PACKAGING
B
= bulk pack
Note
(1) For non-standard requests, please contact application engineering.
www.vishayfoilresistors.com
4
For any questions, contact:
foil@vishaypg.com
Document Number: 63140
Revision: 03-Jan-12
Legal Disclaimer Notice
Vishay Precision Group
Disclaimer
ALL PRODUCTS, PRODUCT SPECIFICATIONS AND DATA ARE SUBJECT TO CHANGE WITHOUT NOTICE.
Vishay Precision Group, Inc., its affiliates, agents, and employees, and all persons acting on its or their
behalf (collectively, “Vishay Precision Group”), disclaim any and all liability for any errors, inaccuracies or
incompleteness contained herein or in any other disclosure relating to any product.
The product specifications do not expand or otherwise modify Vishay Precision Group’s terms and
conditions of purchase, including but not limited to, the warranty expressed therein.
Vishay Precision Group makes no warranty, representation or guarantee other than as set forth in the terms
and conditions of purchase.
To the maximum extent permitted by applicable law, Vishay Precision
Group disclaims (i) any and all liability arising out of the application or use of any product, (ii) any and
all liability, including without limitation special, consequential or incidental damages, and (iii) any and
all implied warranties, including warranties of fitness for particular purpose, non-infringement and
merchantability.
Information provided in datasheets and/or specifications may vary from actual results in different
applications and performance may vary over time. Statements regarding the suitability of products for
certain types of applications are based on Vishay Precision Group’s knowledge of typical requirements that
are often placed on Vishay Precision Group products. It is the customer’s responsibility to validate that a
particular product with the properties described in the product specification is suitable for use in a particular
application.
No license, express, implied, or otherwise, to any intellectual property rights is granted by this document, or
by any conduct of Vishay Precision Group.
The products shown herein are not designed for use in life-saving or life-sustaining applications unless
otherwise expressly indicated. Customers using or selling Vishay Precision Group products not expressly
indicated for use in such applications do so entirely at their own risk and agree to fully indemnify Vishay
Precision Group for any damages arising or resulting from such use or sale. Please contact authorized
Vishay Precision Group personnel to obtain written terms and conditions regarding products designed for
such applications.
Product names and markings noted herein may be trademarks of their respective owners.
Document No.: 63999
Revision: 27-Apr-2011
www.vishaypg.com
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