11
LT1218/LT1219
TYPICAL PERFORMANCE CHARACTERISTICS
U
W
THD + Noise vs
Peak-to-Peak Voltage
Large-Signal Response
VS = ±15V
INPUT VOLTAGE (PEAK-TO-PEAK)
THD
+
NOISE
(%)
10
1
0.1
0.01
0.001
02
4
35
LT1218/19 TPC26
1
VS = ±1.5V
AV = 1
VS = ±2.5V
AV = 1
VS = ±2.5V
AV = –1
VS = ±1.5V
AV = –1
f = 1kHz
RL = 10k
(ALL CURVES)
Small-Signal Response
VS = ±15V
AV = 1
VS = ±15V
LT1218/18 TPC27
AV = 1
VS = ±15V
LT1218/18 TPC28
APPLICATIONS INFORMATION
WU
U
Rail-to-Rail Operation
The LT1218/LT1219 differ from conventional op amps in
the design of both the input and output stages. 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 portions of the input common mode range.
Lateral devices are used in both input stages, eliminating
the need for clamps across the input pins. Each input stage
is trimmed for offset voltage. A complementary output
configuration (Q23 through Q26) is employed to create an
Q24
D7
Q23
Q25
V –
V +
V –
C1
C2
Q26
D8
Q22
Q21
D6
Q17
Q16
Q18
Q15
Q19
Q20
D5
D4
D7
Q11
I1
Q10
Q14
CC
Q13
Q9
Q8
Q7
D2
Q1 Q2
Q5
D1
Q3 Q4
Q6
D3
Q12
OUT
V+
– 300mV
V+
V –
IN+
IN–
LT1218/19 F01
TRIM
SHDN
BIAS
CONTROL
Figure 1. LT1218 Simplified Schematic Diagram