THS4061_16 Datasheet, PDF (16/31 Pages) Texas Instruments – 180-MHz HIGH-SPEED AMPLIFIERS

THS4061, THS4062
180ĆMHz HIGHĆSPEED AMPLIFIERS
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SLOS234E − DECEMBER 1998 − REVISED DECEMBER 2003
APPLICATION INFORMATION
offset nulling
The THS4061 has very low input offset voltage for a high-speed amplifier. However, if additional correction is
required, an offset nulling function has been provided. By placing a potentiometer between terminals 1 and 8
and tying the wiper to the negative supply, the input offset can be adjusted. This is shown in
Figure 26.
VCC+
+
THS4061
_
10 kΩ
0.1 µF
0.1 µF
VCC −
Figure 26. Offset Nulling Schematic
optimizing unity gain response
Internal frequency compensation of the THS406x was selected to provide very wideband performance yet still
maintain stability when operated in a noninverting unity gain configuration. When amplifiers are compensated
in this manner there is usually peaking in the closed loop response and some ringing in the step response for
very fast input edges, depending upon the application. This is because a minimum phase margin is maintained
for the G=+1 configuration. For optimum settling time and minimum ringing, a feedback resistor of 270 Ω should
be used as shown in Figure 27. Additional capacitance can also be used in parallel with the feedback resistance
if even finer optimization is required.
Input
+
THS406x
_
Output
270 Ω
Figure 27. Noninverting, Unity Gain Schematic
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