OPA832IDBVT datasheet(14/30 Pages) NSC

14 / 30 page

OPA832

SBOS266E − JUNE 2003 − REVISED AUGUST 2008

www.ti.com

APPLICATIONS INFORMATION

WIDEBAND VOLTAGE-FEEDBACK

OPERATION

The OPA832 is a fixed-gain, high-speed, voltage-

feedback op amp designed for single-supply operation

(+3V to +10V). It features internal RF and RG resistors

which make it easy to select a gain of +2, +1, and −1

without external resistors.The input stage supports in-

put voltages below ground and to within 1.7V of the pos-

itive supply. The complementary common-emitter out-

put stage provides an output swing to within 25mV of

either supply pin. The OPA832 is compensated to pro-

vide stable operation with a wide range of resistive

loads.

Figure 1 shows the AC-coupled, gain of +2 configura-

tion used for the +5V Specifications and Typical Char-

acteristic Curves. The input impedance matching resis-

tor (66.5

Ω) used for testing is adjusted to give a 50Ω

input match when the parallel combination of the bias-

ing divider network is included. Voltage swings reported

in the Electrical Characteristics are taken directly at the

input and output pins. For the circuit of Figure 1, the to-

tal effective load on the output at high frequencies is

150

Ω || 800Ω. The 332Ω and 499Ω resistors at the non-

inverting input provide the common-mode bias voltage.

Their parallel combination equals the DC resistance at

the inverting input (RF RG), reducing the DC output

offset due to input bias current.

OPA832

S =+5V

OUT

66.5

Ω

499

Ω

VCM =2V

332

Ω

150

Ω

CM =2V

6.8

µF

0.1

µF

0.1

µF

400

Ω

400

Ω

Figure 1. AC-Coupled, G = +2, +5V Single-Supply

Specification and Test Circuit

Figure 2 shows the AC-coupled, gain of +2 configura-

tion used for the +3.3V Specifications and Typical Char-

acteristic Curves. The input impedance matching resis-

tor (66.5

Ω) used for testing is adjusted to give a 50Ω

input match when the parallel combination of the bias-

ing divider network is included. Voltage swings reported

in the Electrical Characteristics are taken directly at the

input and output pins. For the circuit of Figure 2, the to-

tal effective load on the output at high frequencies is

150

Ω || 800Ω. The 887Ω and 258Ω resistors at the non-

inverting input provide the common-mode bias voltage.

Their parallel combination equals the DC resistance at

the inverting input (RF RG), reducing the DC output

offset due to input bias current.

OPA832

S = +3.3V

VOUT

66.5

Ω

887

Ω

CM = 0.75V

258

Ω

150

Ω

CM =0.75V

6.8

µF

0.1

µF

0.1

µF

400

Ω

400

Ω

Figure 2. AC-Coupled, G = +2, +3.3V

Single-Supply Specification and Test Circuit

Figure 3 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 in-

put and output pins. For the circuit of Figure 3, the total

effective load will be 150

Ω || 800Ω. Two optional compo-

nents are included in Figure 3. An additional resistor

(175

Ω) is included in 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

200

Ω source resistance seen at the inverting input (see

the DC Accuracy and Offset Control section). In addi-

tion to the usual 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

optional capacitor will typically improve the 2nd-har-

monic distortion performance by 3dB to 6dB.

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