LT6204 datasheet(12/18 Pages) LINER

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LTC6253-7

62537f

For more information www.linear.com/LTC6253-7

APPLICATIONS INFORMATION

Circuit Description

The LTC6253-7 has 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 differ-

ential 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

inputvoltageapproachesthepositivesupply,thetransistor

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 common mode

range. Also, at the input stage, devices Q17 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.Apairofcomplementarycommonemitterstages,Q14/

Q15, enable the output to swing from rail-to-rail.

Figure 1. LTC6253-7 Simplified Schematic Diagram

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

to V+.

+IN: Non-Inverting Input of Amplifier. Input range from

V– to V+.

V+ : Positive Supply Voltage. Total supply voltage ranges

from 2.5V to 5.25V.

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:AmplifierOutput.Swingsrail-to-railandcantypically

source/sink over 90mA of current at a total supply of 5V.

PIN FUNCTIONS

625234 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

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