LT6011/LT6012

11

sn60112 60112fas

APPLICATIO S I FOR ATIO

impedance at the input, including the source impedance.

Capacitive Loads

The LT6011/LT6012 can drive capacitive loads up to 500pF

in unity gain. The capacitive load driving capability increases

as the amplifier is used in higher gain configurations. A small

series resistance between the output and the load further

increases the amount of capacitance that the amplifier can

drive.

Rail-to-Rail Operation

The LT6011/LT6012 outputs can swing to within millivolts

of either supply rail, but the inputs can not. However, for

most op amp configurations, the inputs need to swing less

than the outputs. Figure 1 shows the basic op amp configu-

rations, lists what happens to the op amp inputs and speci-

fies whether or not the op amp must have rail-to-rail inputs.

Select a rail-to-rail input op amp only when really neces-

sary, because the input precision specifications are usually

inferior.

INPUTS MOVE BY AS MUCH AS

MORE

INPUT MAY NOT HAVE TO BE

RAIL-TO-RAIL

INPUTS MOVE BY AS MUCH AS

OUTPUT

INPUT MUST BE RAIL-TO-RAIL

FOR OVERALL CIRCUIT

RAIL-TO-RAIL PERFORMANCE

OP AMP INPUTS DO NOT MOVE,

BUT ARE FIXED AT DC BIAS

INPUT DOES NOT HAVE TO BE

RAIL-TO-RAIL

–

+

–

+

6011 F01

–

+

Figure 1. Some Op Amp Configurations Do Not Require Rail-to-Rail Inputs to Achieve Rail-to-Rail Outputs

SI PLIFIED SCHE ATIC

6011 SS

Q22

Q16

Q3

Q7

Q8

C

B

A

B

A

Q15

Q1

Q2

D2

D1

Q11

Q17

Q21

Q4

Q6

Q5

C2

Q12

D3

D4

D5

Q14

Q20

Q19

Q13

Q18

R3

R4

R6

R5

R1

500

Ω

R2

500

Ω

C1

C3

+IN

–IN

OUT

Q9

Q10

(One Amplifier)