Application Note 141
October 2013
Risk Assessment Advice for High Reliability Amplifiers
Tim Regan and James Mahoney Introduction
In long life, high reliability systems, supplied power is
provided only to essential circuitry. As a result many of
the unpowered circuits may have voltages applied to inputs and outputs without proper supply biasing. As part
of any diligent system safety risk assessment, a question
often arises; will the unpowered components be damaged,
degraded, or impair circuit performance under these
abnormal operating conditions?
The purpose of this article is to provide advice for what
lies within the pins of several common amplifiers used in
these applications. Most of the amplifiers of interest are the
radiation hard amplifiers so indicated with a device prefix
of RH. Another amplifier, the LT6016, is particularly robust
with over, under and reversed polarity voltage conditions
and is included for reference.
With no power applied to the amplifier, forcing a voltage
between two pins will cause a current to flow. The magnitude of this current differs from pin to pin and device to
device. A curve tracer is used to show the current vs voltage
characteristic when overdriving specific pin combinations.
Referencing these curve trace plots will provide an indication of the magnitude of current flow for a particular …
