In-the-loop compensation method

AN2653

14/22

Table 5 and Table 6 help you to choose the best compensation components for different

gain configuration of either -10 or +11.

However, each case of load can be improved by choosing specific components (seeTable 3

and Table 4).

These tables are very valuable because almost all the follower and gain configuration

applications requiring compensation have capacitive loads in the range of 100 pF to 1 nF.

very good stability.

Figure 24 with the peaking present on closed loop. Both figures show the benefits of

compensation.

Table 5.

Best compensation components for different load capacitor ranges in voltage

Load capacitor range

Minimum gain

margin (dB)

Minimum phase

margin (degree)

10 pF to 100 pF

1

251

16.8

54.9 °

100 pF to 1 nF

1

251

15.8

42.1 °

1 nF to 10 nF

1

631

10.9

27 °

10 nF to 100 nF

1

2500

3.8

18.4 °

Table 6.

Best compensation components for different load capacitor ranges in a gain

Load capacitor range

Minimum gain

margin (dB)

Minimum phase

margin (degree)

10 pF to 100 pF

1000

40

39.2

88.8 °

100 pF to 1 nF

39.8

63

37.2

86.8 °

1 nF to 10 nF

63

251

36.5

70.7 °

10 nF to 100 nF

15.8

631

39.1

63.1 °

Figure 23.

Loop gain

Figure 24.

Measured closed loop gain

Voltage Follower Configuration - Loop Gain

Compensation with the In-the-Loop Technique

-30

-10

10

30

50

70

90

110

130

150

Frequency (Hz)

-270

-240

-210

-180

-150

-120

-90

-60

-30

0

Gain without Compensation

Gain with RIL = 1 kΩ and CIL = 470 pF

Phase without Compensation

Phase with RIL = 1 kΩ and CIL = 470 pF

TS507 :

Vcc = 5 V

Vicm = 2,5 V

T = 25 °C

RL = 10 kΩ

CL = 1 nF

Voltage Follower Configuration - Closed Loop Gain

Compensation with the In-the-Loop Technique

-40

-30

-20

-10

0

10

20

Frequency (Hz)

Gain without CL

Gain with RIL = 1 kΩ and CIL = 470 pF

TS507 :

Vcc = 5 V

Vicm = 2,5 V

T = 25 °C

RL = 10 kΩ

CL = 1 nF

Without Compensation

With In-the-Loop Compensation Technique