LM324, LM324A, LM224, LM2902, LM2902V, NCV2902

http://onsemi.com

6

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.

Figure 2. Large Signal Voltage Follower Response

5.0

ms/DIV

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.

Single Supply

Split Supplies

1

2

3

4

1

2

3

4

Figure 3.

70

60

50

40

30

20

10

0

1.0

10

100

10000

LOAD CAPACITANCE (pF)

Phase Margin

Figure 4. Gain and Phase Margin

1000

70

60

50

40

30

20

10

0

Gain Margin