OPA830 datasheet(22/43 Pages) TI1

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APPLICATIONS INFORMATION

WIDEBAND VOLTAGE-FEEDBACK

1/2

OPA2830

S = +3V

OUT

53.6

Ω

2.26k

Ω

1.13k

Ω

150

Ω

6.8

µF

0.1

µF

0.1

µF

750

Ω

750

Ω

+1V

S/3

1/2

OPA2830

S = +5V

OUT

53.6

Ω

1.5k

Ω

S/2

1.5k

Ω

150

Ω

6.8

µF

0.1

µF

0.1

µF

750

Ω

750

Ω

2.5V

OPA2830

SBOS309D – AUGUST 2004 – REVISED AUGUST 2008.................................................................................................................................................. www.ti.com

high frequencies is 150

Ω || 1500Ω. The 1.13kΩ and

2.26k

Ω resistors at the noninverting input provide the

common-mode

bias

voltage.

Their

parallel

OPERATION

combination equals the DC resistance at the inverting

The OPA2830 is a unity-gain stable, very high-speed

input (RF), reducing the DC output offset due to input

voltage-feedback op amp designed for single-supply

bias current.

operation (+3V to +10V). The input stage supports

input voltages below ground and to within 1.7V of the

positive supply. The complementary common-emitter

output stage provides an output swing to within 25mV

of ground and the positive supply. The OPA2830 is

compensated to provide stable operation with a wide

range of resistive loads.

Figure 70 shows the AC-coupled, gain

configuration used for the +5V Specifications and

Typical Characteristic Curves. For test purposes, the

input impedance is set to 50

Ω with a resistor to

ground. Voltage swings reported in the Electrical

Characteristics are taken directly at the input and

output pins. For the circuit of Figure 70, the total

effective load on the output at high frequencies is

150

Ω

1500

Ω.

The

1.5k

Ω

resistors

the

noninverting input provide the common-mode bias

voltage. Their parallel combination equals the DC

resistance at the inverting input (RF), reducing the DC

output offset due to input bias current.

Figure 71. AC-Coupled, G = +2, +3V Single-Supply

Specification and Test Circuit

Figure 72 shows the DC-coupled, gain of +2, dual

power-supply circuit configuration used as the basis

of the ±5V Electrical Characteristics and Typical

Characteristics.

For

test

purposes,

the

input

impedance is set to 50

Ω with a resistor to ground and

the output impedance is set to 150

Ω with a series

output resistor. Voltage swings reported in the

specifications are taken directly at the input and

output pins. For the circuit of Figure 72, the total

effective load will be 150

Ω || 1.5kΩ. Two optional

components are included in Figure 72. An additional

resistor

(348

Ω) is

included

series

with

the

noninverting input. Combined with the 25

Ω DC

source resistance looking back towards the signal

generator, this gives an input bias current cancelling

resistance that matches the 375

Ω source resistance

seen at the inverting input (see the DC Accuracy and

Figure 70. AC-Coupled, G = +2, +5V Single-Supply

Offset Control section). In addition to the usual

Specification and Test Circuit

power-supply decoupling capacitors to ground, a

0.01

µF capacitor is included between the two

power-supply pins. In practical PC board layouts, this

Figure 71 shows the AC-coupled, gain

optional

capacitor

will

typically

improve

the

configuration used for the +3V Specifications and

2nd-harmonic distortion performance by 3dB to 6dB.

Typical

Characteristic

Curves.

Voltage

swings

reported in the Electrical Characteristics are taken

directly at the input and output pins. For the circuit of

Figure 71, the total effective load on the output at

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