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

VAR

Vishay Foil Resistors

Document Number: 63140

www.vishayfoilresistors.com

Revision: 22-Nov-10

1

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

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.

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.

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 Ω to 100 kΩ

• "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.

• Prototype quantities available in just 5 working days or

sooner. For more information, please contact

foil@vishaypg.com

For better performances please contact us.