TL087 Datasheet, PDF (19/20 Pages) Texas Instruments – JFET-INPUT OPERATIONAL AMPLIFIERS

TL087, TL088, TL287, TL288
JFET-INPUT OPERATIONAL AMPLIFIERS
SLOS082A – D2484, MARCH 1979 – REVISED JANUARY 1993
TYPICAL APPLICATION DATA
input characteristics
These amplifiers are specified with a minimum and a maximum input voltage that, if exceeded at either input,
could cause the device to malfunction.
Because of the extremely high input impedance and resulting low bias current requirements, these amplifiers
are well suited for low-level signal processing; however, leakage currents on printed circuit boards and sockets
can easily exceed bias current requirements and cause degradation in system performance. It is good practice
to include guard rings around inputs (see Figure 45). These guards should be driven from a low-impedance
source at the same voltage level as the common-mode input.
VI
+
VO
VI
–
VO
VO
VI
(a) NONINVERTING AMPLIFIER
(b) INVERTING AMPLIFIER
Figure 45. Use of Guard Rings
(c) UNITY–GAIN AMPLIFIER
noise performance
The noise specifications in op amp circuits are greatly dependent on the current in the first-stage diflferential
amplifier. The low input bias current requirments of these amplifiers result in a very low current noise. This
feature makes the devices especially favorable over bipolar devices when using values of circuit impedance
greater than 50 kΩ.
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