LT1190 Ver la hoja de datos (PDF) - Linear Technology

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Fabricante

LT1190

Ultrahigh Speed Operational Amplifier

Linear Technology 

LT1190

APPLICATIO S I FOR ATIO

Power Supply Bypassing

The LT1190 is quite tolerant of power supply bypassing.

In some applications a 0.1µF ceramic disc capacitor

placed 1/2 inch from the amplifier is all that is required. A

scope photo of the amplifier output with no supply

bypassing is used to demonstrate this bypassing toler-

ance, RL = 1kΩ.

No Supply Bypass Capacitors

In most applications, and those requiring good settling

time, it is important to use multiple bypass capacitors. A

0.1µF ceramic disc in parallel with a 4.7µF tantalum is

recommended. Two oscilloscope photos with different

bypass conditions are used to illustrate the settling time

characteristics of the amplifier. Note that although the

output waveform looks acceptable at 1V/DIV, when ampli-

fied to 1mV/DIV the settling time to 2mV is 4.244µs for the

0.1µF bypass; the time drops to 163ns with multiple

bypass capacitors.

Settling Time Poor Bypass

AV = –1, IN DEMO BOARD, RL = 1kΩ

LT1190 • TA04

Supply bypassing can also affect the response in the

frequency domain. It is possible to see a slight 1dB rise in

the frequency response at 130MHz depending on the gain

configuration, supply bypass, inductance in the supply

leads and printed circuit board layout. This can be further

minimized by not using a socket.

Closed-Loop Voltage Gain vs Frequency

20

VS = ±5V

TA = 25°C

RL = 1k

10

AV = 2

AV = 1

0

–10

–20

100k

1M

10M

100M

1G

FREQUENCY (Hz)

LT1190 • TA05

VOUT

1V/DIV

0V

VOUT

1mV/DIV

SETTLING TIME TO 2mV, AV = –1

SUPPLY BYPASS CAPACITORS = 0.1µF

LT1190 • TA06

Settling Time Good Bypass

VOUT

1V/DIV

0V

VOUT

1mV/DIV

LT1190 • TA07

SETTLING TIME TO 2mV, AV = –1

SUPPLY BYPASS CAPACITORS = 0.1µF + 4.7µF TANTALUM

8

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