isolation amplifier การใช้

• Such a situation does not usually define the need for an isolation amplifier, but rather a differential amplifier.
• Higher frequency common mode voltages create difficulty for many isolation amplifiers due to the parasitic capacitance of the isolation barrier.
• The isolation amplifier contains a voltage-to-frequency converter connected through a transformer to a frequency-to-voltage converter.
• Isolation amplifiers may include isolated power supplies for both the input and output stages, or may use external power supplies on each isolated portion.
• Special isolation amplifier devices include high-voltage insulating barriers between input and output, allowing connection to circuits energized at 1 kV or more.
• However, if the sum of the normal mode and common mode voltages exceeds either the differential amplifier s common mode range, or maximum range without damage then the need for an isolation amplifier is firmly established.
• However, most common mode voltages are a composite of line voltages, so frequencies generally remain in the 50 to 60 Hz region with some harmonic content, well within the rejection range of most isolation amplifiers.
• Other types of differential amplifier include the fully differential amplifier ( similar to the op-amp, but with two outputs ), the instrumentation amplifier ( usually built from three op-amps ), the isolation amplifier ( similar to the instrumentation amplifier, but with tolerance to common-mode voltages that would destroy an ordinary op-amp ), and negative feedback amplifier ( usually built from one or more op-amps and a resistive feedback network ).