7

LT1226

S

APPLICATI

I FOR ATIO

Compensation for Lower Closed-Loop Gains

frequency domain and in the transient response. The

photo of the small signal response with 1000pF load

shows 55% peaking. The large signal response with a

10,000pF load shows the output slew rate being limited by

the short circuit current.

Lag Compensation

S

APPLICATI

TYPICAL

The LT1226 can drive coaxial cable directly, but for best

pulse fidelity the cable should be doubly terminated with

a resistor in series with the output.

Compensation

The LT1226 has a typical gain bandwidth product of 1GHz

which allows it to have wide bandwidth in high gain

configurations (i.e., in a gain of 1000 it will have a

bandwidth of about 1MHz). The amplifier is stable in a

noise gain of 25 so the ratio of the output signal to the

inverting input must be 1/25 or less. Straightforward gain

configurations of +25 or –24 are stable, but there are a few

configurations that allow the amplifier to be stable for

lower signal gains (the noise gain, however, remains 25 or

more). One example is the inverting amplifier shown in the

typical applications sections below. The input signal has a

configuration is equivalent to a gain of –24 as far as the

amplifier is concerned. Lag compensation can also be

used to give a low frequency gain less than 25 with a high

frequency gain of 25 or greater. The example below has a

DC gain of 6, but an AC gain of +31. The break frequency

of the RC combination across the amplifier inputs should

be at least a factor of 10 less than the gain bandwidth of the

amplifier divided by the high frequency gain (in this case

1/10 of 1GHz/31 or 3MHz).

Cable Driving

–

+

200

Ω

LT1226

330pF

5k

LT1226 TA03

1k

LT1226 TA04

R2

50

Ω

IN

V

OUT

V

R1

1.2k

R3

75

Ω

R4

75

Ω

75

CABLE

Ω

LT1226

+

–

–

+

LT1226

LT1226 TA05

LT1226 TA06

–

+

LT1226

300k

300k

1

8

10k

10k

25k

25

Ω

100pF

100pF

LT1097

–

+

LT1226 AI04

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of circuits as described herein will not infringe on existing patent rights.