6

LT1221

f = 5MHz

LT1221 • TPC19

f = 2MHz

LT1221 • TPC20

LT1221 • TPC21

f = 20kHz

f = 5MHz

LT1221 • TPC22

f = 2MHz

LT1221 • TPC23

LT1221 • TPC24

f = 500kHz

The LT1221 is stable in noise gains of 4 or greater and may

be inserted directly into HA2520/2/5, HA2541/2/4, AD817,

AD847, EL2020, EL2044 and LM6361 applications, pro-

vided that the nulling circuitry is removed and the ampli-

fier configuration has a high enough noise gain. The

suggested nulling circuit for the LT1221 is shown in the

following figure.

Layout and Passive Components

The LT1221 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, although low profile sockets can provide reason-

able performance up to 50MHz. 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.

Input Considerations

Bias current cancellation circuitry is employed on the

inputs of the LT1221 so the input bias current and input

LT1221 • AI01

0.1

µF

0.1

µF

5k

3

2

4

7

6

8

1

LT1221

+

–

Offset Nulling