OPA688M

UNITY GAINSTABLE WIDEBAND

VOLTAGE LIMITING AMPLIFIER

SGLS144B − APRIL 2003 − DECEMBER 2006

12

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

dual-supply, non-inverting amplifier

Figure 30 shows a non-inverting gain amplifier for dual-supply operation. This circuit was used for AC

characterization of the OPA688, with a 50-

Ω source, which it matches, and a 500-Ω load. The power-supply

bypass capacitors are shown explicitly in Figures 30 and 31, but will be assumed in the other figures. The limiter

voltages (VH and VL) and their bias currents (IVH and IVL) have the polarities shown.

single-supply, non-inverting amplifier

Figure 31 shows an AC-coupled, non-inverting gain amplifier for single +5V supply operation. This circuit was

used for AC characterization of the OPA688, with a 50W source, which it matches, and a 500-

Ω load. The

power-supply bypass capacitors are shown explicitly in Figures 30 and 31, but will be assumed in the other

figures. The limiter voltages (VH and VL) and their bias currents (IVH and IVL) have the polarities shown. Notice

that the single-supply circuit can use three resistors to set VH and VL, where the dual-supply circuit usually uses

four to reference the limit voltages to ground.

limited output, ADC input driver

Figure 32 shows a simple ADC (Analog-to-Digital Converter) driver that operates on a single supply, and gives

excellent distortion performance. The limit voltages track the input range of the converter, completely protecting

against input overdrive.

OPA688

49.9

Ω

6

I VH

V O

V IN

I VL

−V S =− 5V

3

2

4

7

8

5

R F

402

Ω

R G

402

Ω

500

Ω

0.1 ∝ F

0.1 ∝ F

0.1 ∝ F

174

Ω

3.01k

Ω

1.91k

Ω

3.01k

Ω

1.91k

Ω

0.1 ∝ F

V H = +2V

V L =− 2V

2.2

∝ F

2.2

∝ F

+V S = +5V

Figure 30. DC-Coupled, Dual Supply Amplifier