6

LT1222

LT1222 • TPC19

LT1222 • TPC20

LT1222 • TPC21

LT1222 • TPC22

LT1222 • TPC23

LT1222 • TPC24

f = 5MHz

f = 5MHz

f = 2MHz

f = 2MHz

The LT1222 is stable in noise gains of 10 or greater and

may be inserted directly into HA2520/2/5, HA2541/2/4,

AD817, AD847, EL2020, EL2044 and LM6361 applica-

tions, provided that the nulling circuitry is removed and

the amplifier configuration has a high enough noise gain.

The suggested nulling circuit for the LT1222 is shown in

the following figure.

Layout and Passive Components

The LT1222 amplifier is easy to apply and tolerant of less

than ideal layouts. For maximum performance (for ex-

ample, fast settling time) use a ground plane, short lead

lengths and RF-quality bypass capacitors (0.01

µFto0.1µF).

For high drive current applications use low ESR bypass

capacitors (1

µF to 10µF tantalum). Sockets should be

avoided when maximum frequency performance is re-

quired. For more details see Design Note 50. Feedback

resistors greater than 5k are not recommended because a

pole is formed with the input capacitance which can cause

peaking or oscillations. Stray capacitance on pin 5 should

be minimized. Bias current cancellation circuitry is em-

ployed on the inputs of the LT1222 so the input bias current

and input offset current have identical specifications. For

this reason, matching the impedance on the inputs to

reduce bias current errors is not necessary.

Offset Nulling

LT1222 • AI01

0.1

µF

0.1

µF

5k

3

2

4

7

6

8

1

LT1222

+

–

f = 20kHz

f = 500kHz