LT6002CDHC datasheet(12/20 Pages) LINER

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LT6000/LT6001/LT6002

600012fa

APPLICATIO S I FOR ATIO

The input offset voltage changes depending on which

input stage is active; input offset voltage is trimmed on

both input stages, and is guaranteed to be 600

µV max in

the PNP stage. By trimming the input offset voltage of

both input stages, the input offset voltage over the entire

common mode range (CMRR) is typically 400

µV, main-

taining the precision characteristics of the amplifier.

The input stage of the LT6000/LT6001/LT6002 incorpo-

rates phase reversal protection to prevent wrong polarity

outputs from occurring when the inputs are driven up to

2V below the negative rail. 30k protective resistors are

included in the input leads so that current does not

become excessive when the inputs are forced below V– or

when a large differential signal is applied. Input current

should be limited to 10mA when the inputs are driven

above the positive rail.

Output

The output of the LT6000/LT6001/LT6002 can swing to

within 30mV of the positive rail with no load and within

30mV of the negative rail with no load. When monitoring

input voltages within 30mV of the positive rail or within

30mV of the negative rail, gain should be taken to keep

the output from clipping. The LT6000/LT6001/LT6002

can typically source 10mA on a single 5V supply, sourc-

ing current is reduced to 4mA on a single 1.8V supply as

noted in the electrical characteristics.

The normally reverse-biased substrate diode from the

output to V– will cause unlimited currents to flow when the

output is forced below V–. If the current is transient and

limited to 100mA, no damage will occur.

Start-Up and Output Saturation Characteristics

Micropower op amps are often not micropower during

start-up characteristics or during output saturation. This

can wreak havoc on limited current supplies, in the worst

case there may not be enough supply current available to

take the system up to nominal voltages. Also, when the

output saturates, the part may draw excessive current and

pull down the supplies, compromising rail-to-rail perfor-

mance. Figure 1 shows the start-up characteristics of the

LT6000/LT6001/LT6002 for three limiting cases. The cir-

cuits are shown in Figure 2. One circuit creates a positive

offset forcing the output to come up saturated high.

Another circuit creates a negative offset forcing the output

to come up saturated low, while the last circuit brings the

output up at 1/2 supply. In all cases, the supply current is

well controlled and is not excessive when the output is on

either rail.

SUPPLY VOLTAGE (V)

60012 F01

0.5

1.5

3.5

4.5

2.5

OUTPUT LOW

OUTPUT HIGH

OUTPUT AT VS/2

–

30mV

Output High

–

VS/2

60012 F02

Output at VS/2

–

30mV

Output Low

Figure 1. Start-Up Characteristics

Figure 2. Circuits for Start-Up Characteristics

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