11

OPA2634

®

1/2

OPA2634

+V

S

V

OUT

V

IN

R

3

R

2

R

1

R

4

FIGURE 5. DC Level-Shifting Circuit.

FIGURE 6. Compensated Non-Inverting Amplifier.

frequency of 5MHz, and a –60dB stopband starting at

12MHz. This filter works well on +5V or

±5V supplies, and

needs to be a very low impedance source, such as an op amp.

The filter transfer function was designed using Burr-Brown’s

FilterPro 42 design program (available at www.burr-

brown.com in the Applications section) with a nominal

zero frequency). Note that the parameters were generated at

SECTION NO.

1

1V/V

5.04MHz

1.77

12.6MHz

2

1V/V

5.31MHz

0.64

20.4MHz

3

1V/V

5.50MHz

—

—

TABLE I. Nominal Filter Parameters.

0

–10

–20

–30

–40

–50

–60

–70

–80

Frequency (MHz)

1

10

100

FIGURE 4. Nominal Filter Response.

and output voltage ranges.

The front page circuit is a good example of this type of

+3V supply. This means G = 2.00, and

∆V

• 0.25V = 1.00V. Plugging into the above equations gives:

resistors were changed to the nearest standard values.

NON-INVERTING AMPLIFIER WITH

REDUCED PEAKING

Figure 6 shows a non-inverting amplifier that reduces peak-

to have higher Noise Gain (NG), which reduces the AC

impedance source, such as an op amp. The resistor values

minimize the impact of parasitic impedances.

The components were chosen to give this transfer function.

The 20

Ω resistors isolate the amplifier outputs from capacitive

loading, but affect the response at very high frequencies only.

Figure 4 shows the nominal response simulated by SPICE; it

is very close to the ideal response.

DC LEVEL-SHIFTING

Figure 5 shows a DC-coupled, non-inverting amplifier that

level-shifts the input up to accommodate the desired output

voltage range. Given the desired signal gain (G), and the

the center of its range, the following equations give the

resistor values that produce the best DC offset:

NG = G +

∆V

where:

1/2

OPA2634

V

OUT

V

IN

R

G

R

T

R

F

R

C