LT1499 LINER [Linear Technology], LT1499 Datasheet - Page 11

• Manufacturer Part Number: LT1499
• Description: 10MHz, 6V/us, Dual/Quad Rail-to-Rail Input and Output Precision C-Load Op Amps
• Manufacturer: LINER [Linear Technology]

TYPICAL PERFORMANCE CHARACTERISTICS
APPLICATIONS
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 simplified schematic of the
amplifier. The input stage consists of two differential
amplifiers, a PNP stage (Q1/Q2) and an NPN stage (Q3/
Q4) which are active over different ranges of input com-
mon 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
S
V
IN
L
S
V
IN
L
15V Small-Signal Response
= 5V
= 1
= 1k
= 15V
= 1
= 1k
= 20mV
= 20mV
P-P
P-P
U
AT 50kHz
AT 50kHz
INFORMATION
200ns/DIV
200ns/DIV
U
W
U
W
1498/99 G29
1498/99 G27
U
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
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 configured 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
V
A
V
R
S
V
IN
S
V
IN
L
L
15V Large-Signal Response
= 5V
= 1
= 1k
= 15V
= 1
= 1k
= 4V
= 20V
P-P
P-P
AT 10kHz
AT 10kHz
CM
, between the negative supply to
2 s/DIV
2 s/DIV
1
LT1498/LT1499
, to the current mirror Q6/
1498/99 G28
1498/99 G30
11
CM