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## 596288565013A Datasheet(HTML) 9 Page - Analog Devices

 9 / 16 pageREV. BOP470–9–5005kV1 20V p-p1/4OP4705050kCHANNEL SEPARATION = 20 LOGV1V2/1000V21/4OP470Figure 2. Channel Separation Test Circuit765123+1V+18V4–18V11A+1VBD141312–1VC8910–1VFigure 3. Burn-In CircuitAPPLICATIONS INFORMATIONVoltage and Current NoiseThe OP470 is a very low-noise quad op amp, exhibiting a typi-cal voltage noise of only 3.2 nV÷Hz @ 1 kHz. The exceptionallylow-noise characteristics of the OP470 are in part achieved byoperating the input transistors at high collector currents sincethe voltage noise is inversely proportional to the square root ofthe collector current. Current noise, however, is directly propor-tional to the square root of the collector current. As a result, theoutstanding voltage noise performance of the OP470 is gainedat the expense of current noise performance, which is typical forlow noise amplifiers.To obtain the best noise performance in a circuit, it is vital tounderstand the relationship between voltage noise (en), currentnoise (in), and resistor noise (et).TOTAL NOISE AND SOURCE RESISTANCEThe total noise of an op amp can be calculated by:Eei RennnSt=() + () + ()222where:En = total input referred noiseen = up amp voltage noisein = op amp current noiseet = source resistance thermal noiseRS = source resistanceThe total noise is referred to the input and at the output wouldbe amplified by the circuit gain. Figure 4 shows the relationshipbetween total noise at 1 kHz and source resistance. For RS < 1 kWthe total noise is dominated by the voltage noise of the OP470.As RS rises above 1 kW, total noise increases and is dominatedby resistor noise rather than by voltage or current noise of theOP470. When RS exceeds 20 kW, current noise of the OP470becomes the major contributor to total noise.Figure 5 also shows the relationship between total noise andsource resistance, but at 10 Hz. Total noise increases morequickly than shown in Figure 4 because current noise is inverselyproportional to the square root of frequency. In Figure 5, currentnoise of the OP470 dominates the total noise when RS > 5 kW.From Figures 4 and 5 it can be seen that to reduce total noise,source resistance must be kept to a minimum. In applicationswith a high source resistance, the OP400, with lower currentnoise than the OP470, will provide lower total noise.RS – SOURCE RESISTANCE –1001100100k1010k1kOP11OP400OP471OP470RESISTORNOISE ONLYFigure 4. Total Noise vs. Source Resistance (IncludingResistor Noise) at 1 kHzRS – SOURCE RESISTANCE –1001100100k1010k1kOP11OP400OP471OP470RESISTORNOISE ONLYFigure 5. Total Noise vs. Source Resistance (IncludingResistor Noise) at 10 Hz

## Similar Part No. - 596288565013A

 Manufacturer Part # Datasheet Description Analog Devices 596288565013A 3Mb / 16P Very Low Noise Quad Operational Amplifier REV. B 596288565013A 3Mb / 16P Very Low Noise Quad Operational Amplifier REV. B
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