0

500

1000

1500

2000

2500

0

5

10

15

20

25

1

10

100

FREQUENCY (Hz)

1

10

100

1k

10k

100k

FREQUENCY (Hz)

1

10

100

1k

10k

100k

-60

-95

-90

-85

-80

-75

-70

-65

1M

1

10

100

FREQUENCY (Hz)

1

10

100

1k

10k

100k

1000

LME49713

SNAS386E – SEPTEMBER 2007 – REVISED JUNE 2010

www.ti.com

PSRR

Current Noise

vs

vs

Frequency

Frequency

Equivalent Voltage Noise

Slew Rate

vs

vs

Frequency

Output Voltage

Application Information

GENERAL AMPLIFIER FUNCTION

Voltage feedback amplifiers have a small-signal bandwidth that is a function of the closed-loop gain. Conversely,

the LME49713 current feedback amplifier features a small-signal bandwidth that is relatively independent of the

closed-loop gain. This is shown in Figure 1 where the LME49713’s gain is –1,–2, –5 and –10. Like all current

feedback amplifiers, the LME49713’s closed-loop bandwidth is a function of the feedback resistance value.

POWER SUPPLY BYPASSING AND LAYOUT CONSIDERATIONS

Properly placed and correctly valued supply bypassing is essential for optimized high-speed amplifier operation.

The supply bypassing must maintain a wideband, low-impedance capacitive connection between the amplifier’s

supply pin and ground. This helps preserve high speed signal and fast transient fidelity. The bypassing is easily

accomplished using a parallel combination of a 10

μF tantalum and a 0.1μF ceramic capacitors for each power

supply pin. The bypass capacitors should be placed as close to the amplifier power supply pins as possible.

LME49713 will maintain specified performance with an 1.2k

Ω feedback resistor. Although this value will provide

good results for most applications, it may be advantageous to adjust this value slightly for best pulse response

optimized for the desired bandwidth. In addition to reducing bandwidth, increasing the feedback resistor value

also reduces overshoot in the time domain response.

10

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