Datasheet

TL087, TL088, TL287, TL288
JFET-INPUT OPERATIONAL AMPLIFIERS
SLOS082B – MARCH 1979 – REVISED – JULY 2004
19
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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
easily can 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.
+
−
+
−
+
−
V
O
V
O
V
O
V
I
V
I
(a) NONINVERTING AMPLIFIER (b) INVERTING AMPLIFIER (c) UNITY−GAIN AMPLIFIER
V
I
Figure 45. Use of Guard Rings
noise performance
The noise specifications in operational amplifier circuits are greatly dependent on the current in the first-stage
diflferential amplifier. The low input bias current requirements 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.