OPA602

7

SBOS155A

www.ti.com

POWER-SUPPLY REJECTION vs FREQUENCY

140

1

Frequency (Hz)

10

100

1k

10k

100k

1M

10M

120

100

80

60

40

20

0

+

–

COMMON-MODE REJECTION vs FREQUENCY

140

1

Frequency (Hz)

10

100

1k

10k

100k

1M

10M

120

100

80

60

40

20

0

APPLICATIONS INFORMATION

Unity-gain stability with good phase margin and excellent

output drive characteristics bring freedom from the subtle

problems associated with other high-speed amplifiers. How-

ever, as with any high-speed, wide bandwidth circuitry, care-

ful circuit layout will ensure best performance. Make short,

direct interconnections and avoid stray wiring capacitance—

especially at the inverting input pin.

Power supplies should be bypassed with good high-frequency

capacitors positioned close to the op amp pins. In most cases

0.1

µF ceramic capacitors are adequate. Applications with

heavier loads and fast transient waveforms may benefit from

use of additional 1.0

µF tantalum bypass capacitors.

INPUT BIAS CURRENT GUARDING

Leakage currents across printed circuit boards can easily

exceed the input bias current of the OPA602. A circuit board

“guard” pattern, as shown in Figure 1, is an effective solution

to difficult leakage problems. This guard pattern must be

repeated on all layers of a multilayer board. By surrounding

critical high impedance input circuitry with a low impedance

circuit connection at the same potential, leakage currents will

flow harmlessly to the low-impedance node.

Input bias current may also be degraded by improper han-

dling or cleaning. Contamination from handling parts and

circuit boards may be cleaned with appropriate solvents and

deionized water. Each rinsing operation should be followed

by a 30-minute bake at +85

°C.

Board Layout for Input Guarding:

Guard top and bottom of board.

FIGURE 1. Connection of Input Guard.

2

3

In

Noninverting

6

Out

2

3

In

Inverting

6

Out

2

3

In

Buffer

6

Out

OPA602

OPA602

OPA602