THS4001 Datasheet, PDF (12/16 Pages) Texas Instruments – 270-MHz HIGH-SPEED AMPLIFIER

THS4001
270-MHz HIGH-SPEED AMPLIFIER
SLOS206A– DECEMBER 1997 – REVISED MARCH 1999
APPLICATION INFORMATION
offset nulling
The THS4001 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
of the device and tying the wiper to the negative supply, the input offset can be adjusted. This is shown in
Figure 20.
VCC+
+
THS4001
_
10 kΩ
0.1 µF
0.1 µF
VCC –
Figure 20. Offset Nulling Schematic
optimizing unity gain response
Internal frequency compensation of the THS4001 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 200 Ω should
be used as shown in Figure 21. Additional capacitance can also be used in parallel with the feedback resistance
if even finer optimization is required.
Input
+
THS4001
_
Output
200 Ω
Figure 21. Noninverting, Unity Gain Schematic
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