LT6220/LT6221/LT6222

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A pair of complementary common emitter stages Q14/Q15

that enable the output to swing from rail-to-rail construct

the output stage. The capacitors C2 and C3 form the local

feedback loops that lower the output impedance at high

frequency. These devices are fabricated by Linear

Technology’s proprietary high speed complementary bi-

polar process.

Power Dissipation

The LT6222, with four amplifiers, is housed in a small

16-lead SSOP package and typically has a thermal resis-

die’s junction temperature does not exceed 150°C. The

The power dissipation in the IC is the function of the supply

voltage, output voltage and the load resistance. For a given

occurs when the maximum supply current and the output

voltage is at half of either supply voltage for a given load

PV

I

V

R

D MAX

S

S MAX

S

L

()

()

•/

=

⎛

⎝

⎜

⎞

⎠

⎟

2

2

Example: For an LT6222 in a 16-lead SSOP package

operating on ±5V supplies and driving a 100Ω load, the

worst-case power dissipation is given by:

P

Amp

mA

mW

DMAX

.

/

..

.

=

=+

=

10 1 8

2 5

100

0 018 0 0625

80 5

2

If all four amplifiers are loaded simultaneously, then the

total power dissipation is 322mW.

The maximum ambient temperature at which the part is

allowed to operate is:

= 150°C – (0.322W • 135°C/W) = 106.5°C

APPLICATIO S I FOR ATIO

Input Offset Voltage

The offset voltage will change depending upon which input

stage is active. The PNP input stage is active from the

negative supply rail to 1.2V below the positive supply rail,

then the NPN input stage is activated for the remaining

input range up to the positive supply rail during which the

PNP stage remains inactive. The offset voltage is typically

less than 70µV in the range that the PNP input stage is

active.

Input Bias Current

The LT6220/LT6221/LT6222 employ a patent pending

technique to trim the input bias current to less than 150nA

for the input common mode voltage of 0.2V above the

negative supply rail to 1.2V below the positive rail. The low

input offset voltage and low input bias current of the

LT6220/LT6221/LT6222 provide precision performance

especially for high source impedance applications.

Output

The LT6220/LT6221/LT6222 can deliver a large output

current, so the short-circuit current limit is set around

50mA to prevent damage to the device. Attention must be

paid to keep the junction temperature of the IC below the

absolute maximum rating of 150°C (refer to the Power

Dissipation section) when the output is in continuous

short circuit. The output of the amplifier has reverse-

biased diodes connected to each supply. If the output is

forced beyond either supply, unlimited current will flow

through these diodes. If the current is transient and limited

to several hundred milliamperes, no damage will occur to

the device.

Overdrive Protection

When the input voltage exceeds the power supplies, two

pair of crossing diodes, D1 to D4, will prevent the output

from reversing polarity. If the input voltage exceeds either

power supply by 700mV, diode D1/D2 or D3/D4 will turn

on to keep the output at the proper polarity. For the phase

reversal protection to perform properly, the input current

must be limited to less than 5mA. If the amplifier is