THS3201D datasheet(14/29 Pages) TI

14 / 29 page

THS3201

SLOS416A − JUNE 2003 − REVISED JANUARY 2004

www.ti.com

APPLICATION INFORMATION

WIDEBAND, NONINVERTING OPERATION

The

THS3201

unity

gain

stable

1.8-GHz

current-feedback operational amplifiers, designed to

operate from a

±3.3-V to ±7.5-V power supply.

Figure 50 shows the THS3201 in a noninverting gain of

2V/V

configuration typically used to generate the

performance

curves.

Most

the

curves

were

characterized using signal sources with 50-

Ω source

impedance, and with measurement equipment presenting

a 50-

Ω load impedance. The 49.9-Ω shunt resistor at the

VI terminal in Figure 50 matches the source impedance of

the test generator.

THS3201

768

Ω

49.9

Ω

100 pF

0.1

µF

6.8

µF

−VS

−7.5 V

Ω Source

100 pF

0.1

µF

6.8

µF

+VS

7.5 V

Ω

768

Ω

49.9

Ω

Figure 50. Wideband, Noninverting Gain

Configuration

Unlike voltage-feedback amplifiers, current-feedback

amplifiers are highly dependent on the feedback resistor

RF for maximum performance and stability. Table 1 shows

the optimal gain setting resistors RF and RG at different

gains to give maximum bandwidth with minimal peaking in

the frequency response. Higher bandwidths can be

achieved, at the expense of added peaking in the

frequency response, by using even lower values for RF.

Conversely, increasing RF decreases the bandwidth, but

stability is improved.

Table 1. Recommended Resistor Values for

Optimum Frequency Response

THS3201 RF for AC When Rload = 100 Ω

Gain

(V/V)

Supply Voltage

(V)

RG (Ω)

RF (Ω)

±7.5

—

1.2 k

±5

—

1.2 k

±7.5

768

±5

715

±7.5

154.9

619

±5

143

576

±7.5

54.9

487

±5

51.1

464

−1

±7.5

619

−1

±5

576

−2

±7.5 and ±5

287

576

−5

±7.5 and ±5

110

549

−10

±7.5 and ±5

49.9

499

WIDEBAND, INVERTING GAIN OPERATION

Figure 51 shows the THS3201 is a typical inverting gain

configuration where the input and output impedances and

signal gain from Figure 50 are retained in an inverting

circuit configuration.

THS3201

287

Ω

100 pF

0.1

µF

6.8

µF

−VS

−7.5 V

Ω Source

100 pF

0.1

µF

6.8

µF

+VS

7.5 V

576

Ω

60.4

Ω

49.9

Ω

Figure 51. Wideband, Inverting Gain

Configuration

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