LT1210CSTR データシートの表示（PDF） - Linear Technology

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LT1210CSTR

1.1A, 35MHz Current Feedback Amplifier

Linear Technology 

LT1210

APPLICATI S I FOR

15V

VIN

+

LT1210

– SD

– 15V

ATIO

VOUT

RF

5V

ENABLE

74C906

24k

RG

15V

1210 F02

Figure 2. Shutdown Interface

response. The quiescent current can be reduced to 9mA in

the inverting configuration without much change in re-

sponse. In noninverting mode, however, the slew rate is

reduced as the quiescent current is reduced.

up the turn-off time and ensures that the LT1210 is

completely turned off. Because the pin is referenced to

the positive supply, the logic used should have a break-

down voltage of greater than the positive supply voltage.

No other circuitry is necessary as the internal circuit

limits the Shutdown pin current to about 500µA. Figure

3 shows the resulting waveforms.

RF = 750Ω IQ = 9mA, 18mA, 36mA

RL = 10Ω VS = ±15V

1210 F04a

Figure 4a. Large-Signal Response vs IQ, AV = –1

AV = 1

RF = 825Ω

RL = 50Ω

RPULL-UP = 24k

VIN = 1VP-P

VS = ±15V

1210 F03

Figure 3. Shutdown Operation

For applications where the full bandwidth of the amplifier

is not required, the quiescent current of the device may be

reduced by connecting a resistor from the Shutdown pin

to ground. The quiescent current will be approximately 65

times the current in the Shutdown pin. The voltage across

the resistor in this condition is V+ – 3VBE. For example, a

82k resistor will set the quiescent supply current to 9mA

with VS = ±15V.

The photos in Figures 4a and 4b show the effect of

reducing the quiescent supply current on the large-signal

RF = 750Ω IQ = 9mA, 18mA, 36mA

RL = 10Ω VS = ±15V

1210 F04b

Figure 4b. Large-Signal Response vs IQ, AV = 2

Slew Rate

Unlike a traditional op amp, the slew rate of a current

feedback amplifier is not independent of the amplifier gain

configuration. There are slew rate limitations in both the

input stage and the output stage. In the inverting mode,

and for higher gains in the noninverting mode, the signal

amplitude on the input pins is small and the overall slew

rate is that of the output stage. The input stage slew rate

is related to the quiescent current and will be reduced as

the supply current is reduced. The output slew rate is set

by the value of the feedback resistors and the internal

capacitance. Larger feedback resistors will reduce the

slew rate as will lower supply voltages, similar to the way

1210fa

9

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