LM324, LM324A, LM224, LM2902, LM2902V, NCV2902
CIRCUIT DESCRIPTION
The LM324 series is made using four internally
compensated, two–stage operational amplifiers. The first
stage of each consists of differential input devices Q20 and
Q18 with input buffer transistors Q21 and Q17 and the
differential to single ended converter Q3 and Q4. The first
stage performs not only the first stage gain function but also
performs the level shifting and transconductance reduction
functions. By reducing the transconductance, a smaller
compensation capacitor (only 5.0 pF) can be employed, thus
saving chip area. The transconductance reduction is
accomplished by splitting the collectors of Q20 and Q18.
Another feature of this input stage is that the input common
mode range can include the negative supply or ground, in
single supply operation, without saturating either the input
devices or the differential to single–ended converter. The
second stage consists of a standard current source load
amplifier stage.
V
CC
= 15 Vdc
R
L
= 2.0 kΩ
T
A
= 25°C
1.0 V/DIV
5.0
µs/DIV
Figure 2. Large Signal Voltage Follower Response
Each amplifier is biased from an internal–voltage
regulator which has a low temperature coefficient thus
giving each amplifier good temperature characteristics as
well as excellent power supply rejection.
3.0 V to V
CC(max)
1
2
3
4
V
CC
V
CC
1
2
3
4
V
EE
1.5 V to V
EE(max)
1.5 V to V
CC(max)
V
EE
/Gnd
Single Supply
Figure 3.
Split Supplies
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