OP4711000 For reference, typical source resistances of some signal sources OP11 are listed in Table I. OP400TABLE I.SourceOP471DeviceImpedanceComments100 Strain gauge < 500 W Typically used in OP470O-PEAK NOISE – nV low-frequency applications. RESISTOR Magnetic < 1,500 W Low IB very important to reduce PEAK-TNOISE ONLY tapehead self-magnetization problems when direct coupling is used. OP471 IB can be neglected. 101001k10k100k Magnetic < 1,500 W Similar need for low I RS – SOURCE RESISTANCE – B in direct phonograph coupled applications. OP471 Figure 6. Peak-to-Peak Noise (0.1 Hz to 10 Hz) vs. Source cartridges will not introduce any Resistance (Includes Resistor Noise) self -magnetization problem. Figure 6 shows peak-to-peak noise versus source resistance over Linear variable < 1,500 W Used in rugged servo-feedback the 0.1 Hz to 10 Hz range. Once again, at low values of RS, the differential applications. Bandwidth of voltage noise of the OP471 is the major contributor to peak-to-peak transformer interest is 400 Hz to 5 kHz. noise. Current noise becomes the major contributor as RS increases. The crossover point between the OP471 and the OP400 for *For further information regarding noise calculations, see “Minimization of peak-to-peak noise is at R Noise in Op Amp Applications,” Application Note AN-15. S = 17 W. The OP470 is a lower noise version of the OP471, with a typical noise voltage density of 3.2 nV/÷Hz @ 1 kHz. The OP470 offers lower offset voltage and higher gain than the OP471, but is a slower speed device, with a slew rate of 2 V/ms compared to a slew rate of 8 V/ms for the OP471. R31.24kR1 5OP471C1R2DUT2F5OP27EC4R60.22FR5600k909R10R1165.4k65.4kR4D1D2OP15ER142001N41481N4148C34.99keR90.22FOP15EOUT306kC5R131F5.9kR8 10kC2R120.032F10kGAIN = 50,000 VS =15V Figure 7. Peak-to-Peak Voltage Noise Test Circuit (0.1 Hz to 10 Hz) –8– REV. A