THS4061, THS4062

180-MHz HIGH-SPEED AMPLIFIERS

SLOS234D – DECEMBER 1998 – REVISED FEBRUARY 2000

15

POST OFFICE BOX 655303

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 23.

_

+

THS4061

VCC –

VCC+

0.1

µF

0.1

µF

10 k

Ω

Figure 23. 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 24. Additional capacitance can also be used in parallel with the feedback resistance

if even finer optimization is required.

_

+

THS406x

270

Ω

Input

Output

Figure 24. Noninverting, Unity Gain Schematic