8

®

OPA606

INPUT PROTECTION

Static damage can cause subtle changes in amplifier input

characteristics without necessarily destroying the device. In

precision operational amplifiers (both bipolar and FET types),

this may cause a noticeable degradation of offset voltage and

drift. Static protection is recommended when handling any

precision IC operational amplifier.

If the input voltage exceeds the amplifier’s negative supply

voltage, input current limiting must be used to prevent

damage.

CIRCUIT LAYOUT

Wideband amplifiers require good circuit layout techniques

and adequate power supply bypassing. Short, direct connec-

tions and good high frequency bypass capacitors (ceramic or

tantalum) will help avoid noise pickup or oscillation.

GUARDING AND SHIELDING

As in any situation where high impedances are involved,

careful shielding is required to reduce “hum” pickup in input

leads. If large feedback resistors are used, they should also

be shielded along with the external input circuitry.

Leakage currents across printed circuit boards can easily

exceed the bias current of the OPA606. To avoid leakage

problems, it is recommended that the signal input lead of the

be soldered directly into a printed circuit board, utmost care

must be used in planning the board layout.

A “guard” pattern should completely surround the high

impedance input leads and should be connected to a low

impedance point which is at the signal input potential (see

Figure 3).

FIGURE 3. Connection of Input Guard.

APPLICATIONS CIRCUITS

FIGURE 4. Inverting Amplifier.

FIGURE 5. Noninverting Buffer.

FIGURE 2. Settling Time Test Circuit.

DUT

2

6

Scope

3

0.1%

0.1%

2k

Ω

7

4

2N4416

2N4416

100pF

3k

Ω

2k

Ω

2k

Ω

0.1%

5k

Ω

Summing

Node

V

OUT

G = –1

+15V

–15V

+15V

+5V

–5V

0.1%

5k

Ω

2

3

In

Noninverting

6

Out

2

3

In

Inverting

6

Out

2

3

In

Buffer

6

Out

OPA606

OPA606

OPA606

BOARD LAYOUT

FOR INPUT GUARDING

Guard top and bottom of board.

for sensitive input pins.

de Nemours & Co.

7

6

8

TO-99 Bottom View

3

2

4 5

6

7

8

1

Mini-DIP Bottom View

3

2

4

1

5

Output

+15VDC

10k

Ω

–15VDC

OPA606

BANDWIDTH > 1MHz

T

GAIN = –10V/V

Input

4

1k

Ω

3

2

7

0.1µF

0.1µF

6

Output

+15VDC

–15VDC

OPA606

Input

0.1µF

0.1µF

4

7

2

3

Bandwidth > 12MHz

Gain = +1V/V

R

13

Ω

6