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APPLICATION INFORMATION

Input Offset Voltage Nulling

4.7kW

1kW

V

CC+

OUT

IN-

IN+

V

CC-

+

-

4.7kW

-

+

V

CC-

OUT

V

CC+

10kW

IN-

IN+

(a)STANDARD ADJUSTMENT

(b) ADJUSTMENTWITHIMPROVEDSENSITIVITY

Voltage-Follower Applications

R

F

I

1mA

F £

-

+

V

I

V

O

V

CC-

V

CC

C =20to50pF

F

TLE2027-EP

Excalibur™ LOW-NOISE HIGH-SPEED

PRECISION OPERATIONAL AMPLIFIER

SLOS511 – JUNE 2007

The TLE2027 series offers external null pins that can be used to further reduce the input offset voltage. The

circuits of Figure 45 can be connected as shown if the feature is desired. If external nulling is not needed, the

null pins may be left disconnected.

Figure 45. Input Offset Voltage Nulling Circuits

The TLE2027 circuitry includes input-protection diodes to limit the voltage across the input transistors; however,

no provision is made in the circuit to limit the current if these diodes are forward biased. This condition can occur

when the device is operated in the voltage-follower configuration and driven with a fast, large-signal pulse. It is

recommended that a feedback resistor be used to limit the current to a maximum of 1 mA to prevent degradation

of the device. Also, this feedback resistor forms a pole with the input capacitance of the device. For feedback

resistor values greater than 10 k

Ω, this pole degrades the amplifier phase margin. This problem can be

alleviated by adding a capacitor (20 pF to 50 pF) in parallel with the feedback resistor (see Figure 46).

Figure 46. Voltage Follower

21

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