OPA2613 datasheet(16/36 Pages) TI2

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OPA2614

SBOS305D − JUNE 2004 − REVISED AUGUST 2008

www.ti.com

APPLICATION INFORMATION

WIDEBAND VOLTAGE-FEEDBACK OPERATION

The OPA2614 gives the exceptional AC performance of a

wideband voltage-feedback op amp with a highly linear,

high-power

output

stage.

Requiring

only

6mA/ch

quiescent current, the OPA2614 swings to within 1.0V of

either supply rail and delivers in excess of 280mA at room

temperature. This low-output headroom requirement,

along with supply voltage independent biasing, gives

remarkable single (+5V) supply operation. The OPA2614

delivers greater than 40MHz bandwidth driving a 2VPP

output into 100

Ω on a single +5V supply. Previous boosted

output stage amplifiers typically suffer from very poor

crossover distortion as the output current goes through

zero. The OPA2614 achieves exceptional power gain with

much better linearity. Figure 1 shows the DC-coupled,

gain of +4, dual power-supply circuit configuration used as

the basis of the

±6V Electrical 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

Ω with a series output resistor. Voltage swings reported

in the electrical characteristics are taken directly at the

input and output pins, whereas load powers (dBm) are

defined at a matched 50

Ω load. For the circuit of Figure 1,

the total effective load is 100

Ω || 603Ω = 86Ω.

1/2

OPA2614

+6V

−6V

ΩLoad

Ω

ΩSource

150

Ω

453

Ω

6.8

µF

0.1

µF6.8µF

0.1

µF

−V

Figure 1. DC-Coupled, G = +4, Bipolar Supply,

Specification and Test Circuit

Figure 2 shows the DC-coupled, bipolar supply circuit

configuration used as the basis for the Inverting Gain

−4V/V Typical Characteristics. Key design considerations

of the inverting configuration are developed in the Inverting

Amplifier Operation section.

1/2

OPA2614

+5V

−5V

ΩLoad

Ω

Source

Ω

453

Ω

113

Ω

Power−supply

decoupling

not shown.

208

Ω

Figure 2. DC-Coupled, G = −4, Bipolar Supply,

Specification and Test Circuit

Figure 3 shows the AC-coupled, gain of +4, single-supply

circuit configuration used as the basis of the +5V Electrical

and Typical Characteristics. Though not a rail-to-rail

design, the OPA2614 requires minimal input and output

voltage headroom compared to other very wideband

voltage-feedback op amps. It will deliver a 2.6VPP output

swing on a single +5V supply with greater than 20MHz

bandwidth. The key requirement of broadband single-

supply operation is to maintain input and output signal

swings within the usable voltage ranges at both the input

and the output. The circuit of Figure 3 establishes an input

midpoint bias using a simple resistive divider from the +5V

supply (two 906

Ω resistors). The input signal is then

AC-coupled into this midpoint voltage bias. The input

voltage can swing to within 1.4V of either supply pin, giving

a 2.2VPP input signal range centered between the supply

pins. The input impedance matching resistor (56.2

Ω) used

for testing is adjusted to give a 50

Ω input match when the

parallel combination of the biasing divider network is

included. The gain resistor (RG) is AC-coupled, giving the

circuit a DC gain of +1

which puts the input DC bias

voltage (2.5V) on the output as well. Again, on a single +5V

supply, the output voltage can swing to within 1.1V of either

supply pin while delivering more than 100mA output

current. A demanding 100

Ω load to a midpoint bias is used

in this characterization circuit. The new output stage used

in the OPA2614 can deliver large bipolar output currents

into this midpoint load with minimal crossover distortion,

as shown by the +5V supply, harmonic distortion plots.

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