THS4031 Datasheet, PDF (26/38 Pages) Texas Instruments – 100-MHz LOW-NOISE HIGH-SPEED AMPLIFIERS

THS4031, THS4032
100-MHz LOW-NOISE HIGH-SPEED AMPLIFIERS
SLOS224C – JULY 1999 – REVISED APRIL 2000
APPLICATION INFORMATION
offset nulling
The THS403x has very low input offset voltage for a high speed amplifier. However, if additional correction is
required, the designer can make use of an offset nulling function provided on the THS4031. By placing a
potentiometer between terminals 1 and 8 of the device and tying the wiper to the negative supply, the input offset
can be adjusted. This is shown in Figure 50.
VCC+
+
THS4031
_
10 kΩ
0.1 µF
0.1 µF
VCC –
Figure 50. Offset Nulling Schematic
offset voltage
The output offset voltage (V_OO) is the sum of the input offset voltage (V_IO) and both input bias currents (I_IB) times
the corresponding gains. The following schematic and formula can be used to calculate the output offset
voltage:
RF
IIB–
RG
+
–
VI
+
VO
RS
ƪ ǒ Ǔƫ ƪ ǒ Ǔƫ ^IIB+
+ ) " ₎ ) VOO VIO 1
RF
RG
IIB RS 1
RF
RG
" IIB– RF
Figure 51. Output Offset Voltage Model
26
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265