Datasheet

8
LT1466L/LT1467L
Figure 1. Simplified Schematic
TYPICAL PERFORMANCE CHARACTERISTICS
UW
Q3
D1
C
C
Q4
Q6
1466L/67L F01
Q1
Q8
Q12
Q13
I
1
V
BIAS
Q2
Q5
–IN
+IN
V
+
V
+
V
–
V
–
BUFFER AND
OUTPUT BIAS
C1
C2
OUT
Q7
Q10
Q11
Q9
APPLICATIONS INFORMATION
WUU
U
Rail-to-Rail Operation
The LT1466L/LT1467L differ from conventional op amps
in the design of both the input and output stages. Figure 1
shows a simplified schematic. The input stage consists of
two differential amplifiers, a PNP stage Q1-Q2 and an NPN
stage Q3-Q4, that are active over different portions of the
input common mode range. Each input stage is trimmed
for offset voltage. A complementary output configuration
(Q12-Q13) is employed to create an output stage with rail-
to-rail swing. The devices are fabricated on Linear
Technology’s proprietary complementary bipolar process,
which ensures very similar DC and AC characteristics for
the output devices Q12 and Q13.
First, looking at the input stage, Q5 switches the current
from current source I
1
between the two input stages.
When the input common mode voltage V
CM
is near the
negative supply, Q5 is reverse biased, so the current from
I
1
becomes the tail current for the PNP differential pair
Q1-Q2. At the other extreme, when V
CM
is near the positive
supply, the PNPs Q1-Q2 are biased off. The current from
Large-Signal Response
V
S
= ±5V
V
S
= ±5V
A
V
= 1
1466L/67L G23
FREQUENCY (Hz)
100
CHANNEL SEPARATION (dB)
130
120
110
100
90
80
70
60
50
40
30
1k 10k 100k
V
S
= ±15V
1466L/67L G24
Channel Separation vs Frequency
1466L/67L G22
V
S
= ±2.5V
A
V
= 1
Small-Signal Response
V
S
= ±2.5V