LTC6246CS6 datasheet(13/24 Pages) LINER

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LTC6246/LTC6247/LTC6248

624678fa

applicaTions inForMaTion

Circuit Description

The LTC6246/LTC6247/LTC6248 have an input and output

signal range that extends from the negative power supply

to the positive power supply. Figure 1 depicts a simplified

schematic of the amplifier. The input stage is comprised

of two differential amplifiers, a PNP stage, Q1/Q2, and an

NPN stage, Q3/Q4 that are active over different common

mode input voltages. The PNP stage is active between

the negative supply to nominally 1.2V below the positive

supply. As the input voltage approaches the positive sup-

ply, the transistor Q5 will steer the tail current, I1, to the

current mirror, Q6/Q7, activating the NPN differential pair

and the PNP pair becomes inactive for the remaining input

commonmoderange.Also,attheinputstage,devicesQ17

to Q19 act to cancel the bias current of the PNP input pair.

When Q1/Q2 are active, the current in Q16 is controlled to

be the same as the current in Q1 and Q2. Thus, the base

current of Q16 is nominally equal to the base current of

the input devices. The base current of Q16 is then mirrored

by devices Q17 to Q19 to cancel the base current of the

input devices Q1/Q2. A pair of complementary common

emitter stages, Q14/Q15, enable the output to swing from

rail-to-rail.

Figure 1. LTC6246/LTC6247/LTC6248 Simplified Schematic Diagram

–IN: Inverting Input of Amplifier. Valid input range from V–

to V+.

+IN: Non-Inverting Input of Amplifier. Valid input range

from V– to V+.

V+ : Positive Supply Voltage. Allowed applied voltage

ranges from 2.5V to 5.25V when V– = 0V.

V–:NegativeSupplyVoltage.Typically0V.Thiscanbemade

a negative voltage as long as 2.5V ≤ (V+ – V–) ≤ 5.25V.

SHDN: Active Low Shutdown. Threshold is typically 1.1V

referenced to V–. Floating this pin will turn the part on.

OUT: Amplifier Output. Swings rail-to-rail and can typically

source/sink over 50mA of current at a total supply of 5V.

pin FuncTions

624678 F01

Q15

ESDD5

Q14

BUFFER

AND

OUTPUT BIAS

Q13

Q12

V–

Q11

Q10

VBIAS

Q19

Q18

Q17

ESDD2

V–

ESDD1

V+

ESDD4

V–

ESDD3

V+

Q16

V–

V+

+IN

–IN

ESDD6

OUT

LTC6246CS6 Datasheet(PDF) 13 Page - Linear Technology

LTC6246CS6 Datasheet(HTML) 13 Page - Linear Technology

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