LT1498IS8 Linear Technology, LT1498IS8 Datasheet - Page 13

• Manufacturer Part Number: LT1498IS8
• Description: IC,Operational Amplifier,DUAL,BIPOLAR,SOP,8PIN,PLASTIC
• Manufacturer: Linear Technology

TYPICAL PERFORMANCE CHARACTERISTICS
APPLICATIONS INFORMATION
Rail-to-Rail Input and Output
The LT1498/LT1499 are fully functional for an input and
output signal range from the negative supply to the posi-
tive supply. Figure 1 shows a simplifi ed schematic of the
amplifi er. The input stage consists of two differential am-
plifi ers, a PNP stage (Q1/Q2) and an NPN stage (Q3/Q4)
which are active over different ranges of input common
mode voltage. A complementary common emitter output
stage (Q14/Q15) is employed allowing the output to swing
from rail-to-rail. The devices are fabricated on Linear
Technology’s proprietary complementary bipolar process
to ensure very similar DC and AC characteristics for the
output devices (Q14/Q15).
V
A
V
R
V
A
V
R
5V Small-Signal Response
±15V Small-Signal Response
S
V
IN
S
V
IN
L
L
= 5V
= 1
= 1k
= 15V
= 1
= 1k
= 20mV
= 20mV
P-P
P-P
AT 50kHz
AT 50kHz
200ns/DIV
200ns/DIV
14989 G29
14989 G27
The PNP differential input pair is active for input common
mode voltages, V
approximately 1.3V below the positive supply. As V
moves further toward the positive supply, the transistor
(Q5) will steer the tail current, I
(Q6/Q7) activating the NPN differential pair, and the PNP
differential pair becomes inactive for the rest of the input
common mode range up to the positive supply.
The output is confi gured with a pair of complementary
common emitter stages that enables the output to swing
from rail to rail. Capacitors (C1 and C2) form local
feedback loops that lower the output impedance at high
frequencies.
5V Large-Signal Response
V
A
V
R
±15V Large-Signal Response
V
A
V
R
S
V
IN
S
V
IN
L
L
= 5V
= 1
= 1k
= 15V
= 1
= 1k
= 4V
= 20V
P-P
P-P
CM
AT 10kHz
AT 10kHz
, between the negative supply to
2μs/DIV
2μs/DIV
LT1498/LT1499
1
, to the current mirror
14989 G28
14989 G30
13
14989fe
CM