Precision Isolation Amplifier High CMV/CMR, 15V Floating
Model 277
FEATURES Versatile Op Amp Front End: Inverting, Non-Inverting, Differential Applications Low Nonlinearity: 0.025% max, Model 277K Low Input Offset Voltage Drift: 1V/C max, Model 277K Floating Power Output: 15V @ 15mA High CMR: 160dB min @ dc High CMV: 3500V rms APPLICATIONS Programmable Gain Isolated Amplifier Isolated Power Source and Amplifier for Bridge Measurements Instrumentation Amplifier Instrumentation Grade Process Signal Isolator Current Shunt Measurements GENERAL DESCRIPTION Model 277 is a versatile isolation amplifier which combines a highperformance, uncommitted operational amplifier front end with a precision, isolated output stage and a floating power supply section. This configuration, shown in Figure 1, makes the 277 ideally suited to instrumentation applications where the need for various forms of signal conditioning, high CMV protection and isolated transducer power requirements are encountered. The input stage is a low drift (1V/C max, model 277K) differential op amp that may be connected for use in inverting, non-inverting and differential configurations. The circuitry employed around the operational amplifier input stage can be designed by the user to suit each application's particular signal processing needs. A full 10V signal range is available at the output of the front-end amplifier. output stage's low nonlinearity (0.05%, models 277J/A and 0.025% model 277K), these high CMR and CMV ratings facilitate accurate measurements in the presence of noisy electrical equipment such as motors and relays. In addition, model 277A offers a -25C to +85C rated operating temperature range. All versions of model 277 have a 10 volt output range. The floating power supply section provides isolated 15 volt outputs capable of delivering currents up to 15mA. This feature permits model 277 to power transducers and auxiliary isolated circuitry, thereby eliminating the need for a separate isolated DC/DC converter. All of the features of the model 277 isolation amplifier are packaged in a compact (3" x 2.2" x 0.59") module. As an assurance of high performance reliability, every model 277 is factory tested for CMV rating by application of 3500V rms (4900V peak) between input and output common terminals for one minute (meets NEMA and CSA requirements for 660Vrms service.) In addition, the 277 has a calculated MTBF of 133,000 hours.
Figure 1. Model 277 Functional Block Diagram
The isolated output stage includes a special modulator/demodulator technique which provides the 277 with l60dB minimum DC common mode rejection between input and output common and an input-tooutput CMV rating of 3500V rms. When combined with the
Information furnished by Intronics is believed to be accurate and reliable. However, no responsibility is assumed by Intronics for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intronics.
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