THS4001

270-MHz HIGH-SPEED AMPLIFIER

SLOS206A– DECEMBER 1997 – REVISED MARCH 1999

12

POST OFFICE BOX 655303

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.

_

+

THS4001

VCC –

VCC+

0.1

µF

0.1

µF

10 k

Ω

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.

_

+

THS4001

200

Ω

Input

Output

Figure 21. Noninverting, Unity Gain Schematic