TL087, TL088, TL287, TL288

JFET-INPUT OPERATIONAL AMPLIFIERS

SLOS082B – MARCH 1979 – REVISED – JULY 2004

6

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

typical values

Typical values as presented in this data sheet represent the median (50% point) of device parametric

performance.

input bias and offset current

At the picoamp bias current level typical of these JFET operational amplifiers, accurate measurement of the bias

current becomes difficult. Not only does this measurement require a picoammeter, but test socket leakages can

easily exceed the actual device bias currents. To accurately measure these small currents, Texas Instruments

uses a two-step process. The socket leakage is measured using picoammeters with bias voltages applied, but

with no device in the socket. The device then is inserted in the socket and a second test that measures both

the socket leakage and the device input bias current is performed. The two measurements then are subtracted

algebraically to determine the bias current of the device.