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LT1806/LT1807

18067fc

Rail-to-Rail Characteristics

The LT1806/LT1807 have input and output signal range that

covers from negative power supply to positive power sup-

ply. Figure 1 depicts a simpliﬁed schematic of the ampliﬁer.

The input stage is comprised of two differential ampliﬁers,

a PNP stage Q1/Q2 and a NPN stage Q3/Q4 that are active

over different ranges of common mode input voltage. The

PNP differential pair is active between the negative supply

to approximately 1.5V below the positive supply. As the

input voltage moves closer toward the positive supply, the

transistor Q5 will steer the tail current I1 to the current

mirror Q6/Q7, activating the NPN differential pair. The PNP

pair becomes inactive for the rest of the input common

mode range up to the positive supply.

APPLICATIONS INFORMATION

A pair of complementary common emitter stages Q14/Q15

that enable the output to swing from rail to rail constructs

the output stage. The capacitors C1 and C2 form the

local feedback loops that lower the output impedance at

high frequency. These devices are fabricated on Linear

Technology’s proprietary high speed complementary

bipolar process.

Power Dissipation

The LT1806/LT1807 ampliﬁers combine high speed with

large output current in a small package, so there is a need

to ensure that the die’s junction temperature does not

exceed 150°C. The LT1806 is housed in an SO-8 package

or a 6-lead SOT-23 package and the LT1807 is in an SO-8

Q10

Q13

Q15

OUT

Q11

Q12

VBIAS

ESDD2

ESDD1

+IN

–IN

V–

ESDD3

ESDD4

V+

V–

Q14

18067 F01

V–

BUFFER

AND

OUTPUT BIAS

Q17

Q16

ESDD5

SHDN

V+

V–

100k

40k

V+

V–

ESDD6

BIAS

GENERATION

Figure 1. LT1806 Simpliﬁed Schematic Diagram

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