Welcome to the
ACamp(TM) AC-coupled Amplifier Home Page

ACamp Amplifiers are AC-coupled instrumentation amplifiers that offer unsurpassed performance for a broad range of measurement applications (biomedical, analog, analytical, ...) as well as amplifier products (audio amplifier, ...). ACamp amplifiers are the only high performance instrumentation amplifiers with true AC-coupled inputs because revolutionary patented designs (U.S. Patent 5,300,896) overcome significant performance limitations produced by all previous AC-coupled amplifier designs. Only ACamp amplifiers simultaneously offer true AC-coupled inputs, very high input impedance, high CMRR, and wide bandwidth.

Why Use AC-coupled Differential Amplifiers?

• All Biomedical Signals are Analog Differential Signals - essentially all biomedical measurements involve selectively amplifying small differential analog signals that are contained in large common-mode signals. Even single-ended biomedical measurements must be made relative to a reference (or ground) electrode, which produces a differential measurement configuation. Only an AC-coupled differential amplifier will selectively amplify a small time varying analog biomedical signal while rejecting common mode signals, DC (and low frequency) signals, and DC input bias currents. In addition, since the AC-coupled inputs block low frequency signals, low frequency amplifier noise is reduced, which significantly decreases total amplifier output noise. Similar advantages also apply to other amplifier systems including audio amplifiers, analog amplifiers, etc.
  
• No DC Bias Current - AC-coupled amplifiers with true AC-coupled inputs have capacitors on the inputs that form high pass filters. In addition to rejecting DC and low frequency signals, the input capacitors also block all DC bias currents from flowing across the amplifier inputs. One advantage is that blocking input DC bias currents eliminates double layer charging across the electrode surface of an input transducer, which significantly increases the transfer of analog biomedical signals across the tissue/transducer interface. Input capacitors also create added patient safety during clinical measurements. Similar advantages also apply to other analog amplifier systems including audio amplifier.

Why Use ACamp(TM) AC-coupled Amplifiers?

• Very High Input Impedance and CMRR - a revolutionary patented design (U.S. Patent 5,300,896) results in the first AC-coupled amplifier that can simultaneously produce the three most desirable features for a biomedical or analog amplifier: (1) true AC-coupled inputs, (2) very high input impedance, and (3) very high CMRR. All other AC-coupled amplifier designs cause significantly degraded input impedance, degraded CMRR, or both. For this reason, ACamp amplifiers are the only available high performance AC-coupled differential amplifiers.
  
• True AC-coupled Inputs - all ACamp amplifiers have true AC-coupled inputs, which means the inputs are connected to capacitors that form high pass filters to block DC and low frequency signals. All other amplifiers that have true AC-coupled inputs produce significantly degraded input impedance, degraded CMRR, or typically both. Many amplifiers that claim to be AC-coupled do not actually have true AC-coupled inputs but instead filter low frequency signals somewhere else in the amplifier; these are still DC-coupled amplifiers with all the problems described above for DC input signals. Only ACamp AC-coupled amplifiers offer true AC-coupled inputs in a high performance differential amplifier or instrumentation amplifier.