Datasheet LT1007, LT1037 (Analog Devices) - 10

LT1007/LT1037
U U W U APPLICATIONS INFORMATION
As with all operational amplifiers when RF > 2k, a pole will electric effects in excess of a few nanovolts, which be created with RF and the amplifier’s input capacitance, would invalidate the measurements. creating additional phase shift and reducing the phase 3. Sudden motion in the vicinity of the device can also margin. A small capacitor (20pF to 50pF) in parallel with RF “feedthrough” to increase the observed noise. will eliminate this problem. A noise voltage density test is recommended when mea-
Noise Testing
suring noise on a large number of units. A 10Hz noise The 0.1Hz to 10Hz peak-to-peak noise of the LT1007/ voltage density measurement will correlate well with a LT1037 is measured in the test circuit shown (Figure 5a). 0.1Hz to 10Hz peak-to-peak noise reading since both The frequency response of this noise tester (Figure 5b) results are determined by the white noise and the location indicates that the 0.1Hz corner is defined by only one zero. of the 1/f corner frequency. The test time to measure 0.1Hz to 10Hz noise should not Current noise is measured in the circuit shown in Figure 6 exceed ten seconds, as this time limit acts as an additional and calculated by the following formula: zero to eliminate noise contributions from the frequency band below 0.1Hz.  1/2 2 2 Measuring the typical 60nV peak-to-peak noise perfor-  e 130nV ( ) −( • ) no 101  mance of the LT1007/LT1037 requires special test   in = precautions: M (1 Ω)( ) 101 1. The device should be warmed up for at least five minutes. As the op amp warms up, its offset voltage 100k changes typically 3µV due to its chip temperature increasing 10°C to 20°C from the moment the power 100Ω 500k – supplies are turned on. In the ten-second measurement LT1007 eno interval these temperature-induced effects can easily 500k +LT1037 exceed tens of nanovolts. 1007/37 F06 2. For similar reasons, the device must be well shielded
Figure 6
from air currents to eliminate the possibility of thermo- 0.1µF 100 90 100k 80 10Ω – * 2k 70 LT1007 + 22µF +LT1037 4.3k SCOPE 60 LT1001 × 1 GAIN (dB) 4.7µF R – IN = 1M 2.2µF 110k 50 VOLTAGE GAIN 100k = 50,000 40 *DEVICE UNDER TEST 24.3k 0.1µF 30 NOTE: ALL CAPACITOR VALUES ARE FOR 1007/37 F05a 0.01 0.1 1 10 100 NONPOLARIZED CAPACITORS ONLY FREQUENCY (Hz) 1007/37F05b
Figure 5a. 0.1Hz to 10Hz Noise Test Circuit Figure 5b. 0.1Hz to 10Hz Peak-to- Peak Noise Tester Frequency Response
sn100737 100737fbs 10