Datasheet OP470 (Analog Devices) - 10

OP470
Figure 6 shows peak-to-peak noise versus source resistance over
Table I.
the 0.1 Hz to 10 Hz range. Once again, at low values of RS, the voltage noise of the OP470 is the major contributor to peak-to-peak
Device
noise with current noise the major contributor as R
Source Impedance Comments
S increases. The crossover point between the OP470 and the OP400 for Strain gage <500 W Typically used in peak-to-peak noise is at RS = 17 kW. low frequency applications. The OP471 is a higher speed version of the OP470, with a slew Magnetic <1500 W Low IB very important to reduce rate of 8 V/ms. Noise of the OP471 is only slightly higher than tapehead self-magnetization problems the OP470. Like the OP470, the OP471 is unity-gain stable. when direct coupling is used. OP470 IB can be neglected.
1000 OP11
Magnetic <1500 W Similar need for low IB in direct phonograph coupled applications. OP470
OP400
cartridges will not introduce any self- magnetization problem.
OP471
Linear variable <1500 W Used in rugged servo-feedback
100
differential applications. Bandwidth of
OP470
transformer interest is 400 Hz to 5 kHz.
O-PEAK NOISE – nV/ Hz RESISTOR
For further information regarding noise calculations, see “Minimization of Noise
NOISE ONLY
in Op Amp Applications,” Application Note AN-15.
PEAK-T NOISE MEASUREMENTS— PEAK-TO-PEAK VOLTAGE NOISE 10 100 1k 10k 100k
The circuit of Figure 7 is a test setup for measuring peak-to-peak
RS – SOURCE RESISTANCE –
voltage noise. To measure the 200 nV peak-to-peak noise speci- Figure 6. Peak-To-Peak Noise (0.1 Hz to 10 Hz) vs. Source fication of the OP470 in the 0.1 Hz to 10 Hz range, the following Resistance (Includes Resistor Noise) precautions must be observed: For reference, typical source resistances of some signal sources 1. The device must be warmed up for at least five minutes. As are listed in Table I. shown in the warm-up drift curve, the offset voltage typi- cally changes 5 mV due to increasing chip temperature after power-up. In the 10-second measurement interval, these temperature-induced effects can exceed tens of nanovolts. 2. For similar reasons, the device must be well-shielded from air currents. Shielding also minimizes thermocouple effects. 3. Sudden motion in the vicinity of the device can also “feedthrough” to increase the observed noise.
R3 1.24k R1 5 OP470 C1 R2 DUT 2 F 5 OP27E C4 R6 0.22 F R5 600k 909 R10 R11 65.4k 65.4k R4 D1 D2 OP15E R14 200 1N4148 1N4148 C3 4.99k e R9 0.22 F OP15E OUT 306k C5 R13 1 F 5.9k R8 10k C2 R12 0.032 F 10k GAIN = 50,000 VS = 5V
Figure 7. Peak-To-Peak Voltage Noise Test Circuit (0.1 Hz to 10 Hz) –10– REV. B Document Outline FEATURES GENERAL DESCRIPTION PIN CONNECTIONS SIMPLIFIED SCHEMATIC SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE Typical Performance Characteristics APPLICATIONS INFORMATION Voltage and Current Noise TOTAL NOISE AND SOURCE RESISTANCE NOISE MEASUREMENTS— PEAK-TO-PEAK VOLTAGE NOISE NOISE MEASUREMENT—NOISE VOLTAGE DENSITY NOISE MEASUREMENT—CURRENT NOISE DENSITY CAPACITIVE LOAD DRIVING AND POWER SUPPLY CONSIDERATIONS UNITY-GAIN BUFFER APPLICATIONS 50k APPLICATIONS Low Noise Amplifier DIGITAL PANNING CONTROL SQUELCH AMPLIFIER FIVE-BAND LOW-NOISE STEREO GRAPHIC EQUALIZER OUTLINE DIMENSIONS Revision History