7

LT1225

S

APPLICATI

I FOR ATIO

domain and in the transient response. The photo of the

small-signal response with 1000pF load shows 50% peak-

ing. The large-signal response with a 10,000pF load shows

the output slew rate being limited by the short-circuit

current.

Lag Compensation

Wein Bridge Oscillator

The LT1225 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 LT1225 has a typical gain-bandwidth product of

150MHz which allows it to have wide bandwidth in high

gain configurations (i.e., in a gain of 10 it will have a

bandwidth of about 15MHz). The amplifier is stable in a

noise gain of 5 so the ratio of the output signal to the

inverting input must be 1/5 or less. Straightforward gain

configurations of 5 or –4 are stable, but there are a few

configurations that allow the amplifier to be stable for

lower signal gains (the noise gain, however, remains 5 or

more). One example is the summing amplifier shown in

the typical applications section below. Each input signal

this configuration is equivalent to a gain of –4 as far as the

amplifier is concerned. Lag compensation can also be

used to give a low frequency gain less than 5 with a high

frequency gain of 5 or greater. The example below has a

DC gain of one, but an AC gain of 5. The break frequency

of the RC combination across the amplifier inputs should

be approximately a factor of 10 less than the gain band-

width of the amplifier divided by the high frequency gain

(in this case 1/10 of 150MHz/5 or 3MHz).

S

APPLICATI

TYPICAL

Cable Driving

Summing Amplifier

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.

LT1225 AI04

LT1225 TA04

R2

250

Ω

IN

V

OUT

V

R1

1k

R3

75

Ω

R4

75

Ω

75

CABLE

Ω

LT1225

+

–

–

+

500

Ω

LT1225

100pF

2k

LT1225 TA03

–

+

LT1225

100pF

1MHz

LT1225 TA05

430

Ω

100pF

1.5k

1.5k

#327

LAMP

–

+

LT1225

LT1225 TA06

4