LT1677CS8 datasheet(9/16 Pages) LINER

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LT1677

APPLICATIO S I FOR ATIO

General

The LT1677 series devices may be inserted directly into

OP-07, OP-27, OP-37 and sockets with or without removal

of external compensation or nulling components. In addi-

tion, the LT1677 may be fitted to 741 sockets with the

removal or modification of external nulling components.

Rail-to-Rail Operation

To take full advantage of an input range that can exceed

the supply, the LT1677 is designed to eliminate phase

reversal. Referring to the photographs shown in Figure 1,

the LT1677 is operating in the follower mode (AV = +1) at

a single 3V supply. The output of the LT1677 clips cleanly

and recovers with no phase reversal. This has the benefit

of preventing lock-up in servo systems and minimizing

distortion components.

Offset Voltage Adjustment

The input offset voltage of the LT1677 and its drift with

temperature are permanently trimmed at wafer

testing to a low level. However, if further adjustment of

VOS is necessary, the use of a 10kΩ nulling potentiometer

will not degrade drift with temperature. Trimming to a

value other than zero creates a drift of (VOS/ 300)µV/°C,

e.g., if VOS is adjusted to 300µV, the change in drift will be

µV/°C (Figure 2).

The adjustment range with a 10k

Ω pot is approximately

±2.5mV. If less adjustment range is needed, the sensitiv-

ity and resolution of the nulling can be improved by using

a smaller pot in conjunction with fixed resistors. The

example has an approximate null range of

±200µV

(Figure 3).

Input = – 0.5V to 3.5V

LT1677 Output

– 0.5V

1577 F01a

– 0.5V

1577 F01b

Figure 1. Voltage Follower with Input Exceeding the Supply Voltage (VS = 3V)

Figure 3. Improved Sensitivity Adjustment

Figure 2. Standard Adjustment

1677 F02

10k

OUTPUT

INPUT

15V

–15V

LT1677

1677 F03

4.7k

OUTPUT

7 6

15V

–15V

LT1677

4.7k

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