LTC6252 Linear Technology, LTC6252 Datasheet - Page 13

• Manufacturer Part Number: LTC6252
• Description: 3.5mA Power Efficient Rail-to-Rail I/O Op Amps
• Manufacturer: Linear Technology

DataSheet.in
–IN: Inverting Input of Amplifi er. Input range from V
to V
+IN: Non-Inverting Input of Amplifi er. Input range from
V
V
from 2.5V to 5.25V.
APPLICATIONS INFORMATION
Circuit Description
The LTC6252/LTC6253/LTC6254 have an input and output
signal range that extends from the negative power supply
to the positive power supply. Figure 1 depicts a simplifi ed
schematic of the amplifi er. The input stage is comprised
of two differential amplifi ers, 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, I
current mirror, Q6/Q7, activating the NPN differential pair
PIN FUNCTIONS
V
V
–
+
+
–
Q16
+
: Positive Supply Voltage. Total supply voltage ranges
to V
+
.
I
2
+
.
+IN
–IN
Q17
ESDD1
ESDD4
Q18
V
V
+
–
V
V
–
+
D6
D5
ESDD2
ESDD3
Figure 1. LTC6252/LTC6253/LTC6254 Simplifi ed Schematic Diagram
Q19
D8
D7
Q4
Q7
Q3
1
, to the
Q5
Q6
–
V
BIAS
Q1
V
a negative voltage as long as 2.5V ≤ (V
SHDN: Active Low Shutdown. Threshold is typically 1.1V
referenced to V
OUT: Amplifi er Output. Swings rail-to-rail and can typically
source/sink over 90mA of current at a total supply of 5V.
+
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. A pair of complementary common
emitter stages, Q14/Q15, enable the output to swing from
rail-to-rail.
LTC6252/LTC6253/LTC6254
–
: Negative Supply Voltage. Typically 0V. This can be made
Q2
I
1
Q10
–
Q11
. Floating this pin will turn the part on.
Q9
R1
R3
Q12
Q8
R2
R4
C
C
+
V
OUTPUT BIAS
Q13
–
R5
BUFFER
I
3
AND
+
– V
C2
C1
–
) ≤ 5.25V.
625234 F01
Q15
Q14
13
ESDD5
ESDD6
625234f
OUT