仪表放大器——可避免常见的设计陷阱

仪表放大器——可避免常见的设计陷阱

Instrumentation Amplifiers—avoiding a common pitfall
Bruce Trump
The instrumentation amplifier (IA) is an integrated combination of op amps
and feedback resistors used to accurately acquire and amplify signals.
    A common mistake in using these versatile amplifiers is to fail to
provide a path for input bias current. For 25 years we’ve been showing a
diagram to highlight the necessary input biasing required for proper
operation but designers seem to miss it. Perhaps it’s the
name—instrumentation amplifier.  It sounds as if it is laboratory equipment
like an oscilloscope or spectrum analyzer, complete with ready-to-use
inputs. Well, that’s almost true but it requires a bit more care.
Each input connects directly to the base of a bipolar t