OPA4197IPWR datasheet(23/56 Pages) TI2

23 / 56 page

Cload

Vin

Vout

+Vs

Riso

-Vs

Capacitive Load (pF)

30 40 50 70 100

200 300

500 700 1000

2000

RISO = 0 :

RISO = 25 :

RISO = 50 :

Capacitive Load (pF)

30 40 50 70 100

200 300

500 700 1000

2000

RISO = 0 :

RISO = 25 :

RISO = 50 :

OPA197, OPA2197, OPA4197

www.ti.com

SBOS737C – JANUARY 2016 – REVISED MARCH 2018

Product Folder Links: OPA197 OPA2197 OPA4197

Submit Documentation Feedback

Figure 47. Small-Signal Overshoot vs Capacitive Load

(100-mV Output Step, G = –1 V/V)

Figure 48. Small-Signal Overshoot vs Capacitive Load

(100-mV Output Step, G = 1 V/V)

For additional drive capability in unity-gain configurations, improve capacitive load drive by inserting a small

(10-Ω to 20-Ω) resistor, RISO, in series with the output, as shown in Figure 49. This resistor significantly reduces

ringing while maintaining dc performance for purely capacitive loads. However, if there is a resistive load in

parallel with the capacitive load, a voltage divider is created, introducing a gain error at the output and slightly

reducing the output swing. The error introduced is proportional to the ratio RISO / RL, and is generally negligible at

low output levels. A high capacitive load drive makes the OPA197 well suited for applications such as reference

buffers, MOSFET gate drives, and cable-shield drives. The circuit shown in Figure 49 uses an isolation resistor,

RISO, to stabilize the output of an op amp. RISO modifies the open-loop gain of the system for increased phase

margin, and results using the OPA197 are summarized in Table 3. For additional information on techniques to

optimize and design using this circuit, TI Precision Design TIDU032 details complete design goals, simulation,

and test results.

Figure 49. Extending Capacitive Load Drive with the OPA197

Table 3. OPA197 Capacitive Load Drive Solution Using Isolation Resistor Comparison of Calculated and

Measured Results

PARAMETER

VALUE

Capacitive Load

100 pF

1000 pF

0.01 µF

0.1 µF

1 µF

Phase Margin

45°

60°

45°

60°

45°

60°

45°

60°

45°

60°

RISO (Ω)

47.0

360.0

24.0

100.0

20.0

51.0

6.2

15.8

2.0

4.7

Measured

Overshoot (%)

23.2 8.6

10.4

22.5

9.0

22.1

8.7

23.1

8.6

21.0

8.6

Calculated PM

45.1°

58.1°

45.8°

59.7°

46.1°

60.1°

45.2°

60.2°

47.2°

60.2°

For step-by-step design procedure, circuit schematics, bill of materials, printed circuit board (PCB) files,

simulation results, and test results, refer to TI Precision Design TIDU032, Capacitive Load Drive Solution using

an Isolation Resistor .

OPA4197IPWR Datasheet(PDF) 23 Page - Texas Instruments

OPA4197IPWR Datasheet(HTML) 23 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

Datasheet Download

Link URL