Saturday, September 20, 2014
Single Supply Instrumentation Amplifier
Potentiometer P1 is used for optimum d.c. CMR adjustment, and capacitor C1 is used to optimize a.c. CMR. With circuit values as shown, circuit CMR is better than 80 dB over the frequency range of 20 Hz to 20 kHz. Circuit referred-to-input (RTI) noise in the 0.1 Hz to 10 Hz band is exemplary at 0.45 µVpp. Resistors R5 and R6 protect the inputs of the op amps against over-voltages. Capacitor C2 may be included to limit the bandwidth. Its value should be adjusted depending on the required closed-loop bandwidth of the circuit. The R4-C2 time constant creates a pole at a frequency, f3dB, equal to f3dB=1/2πR4C2. With a value of C2 of 12 pF, the bandwidth is about 500 kHz. The amplifier draws a current of about 2mA.
Labels:
amplifier,
Instrumentation,
single,
supply
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