1

LT1166

Power Output Stage

Automatic Bias System

FEATURES

s

Set Class AB Bias Currents

s

Eliminates Adjustments

s

s

Corrects for Device Mismatch

s

Simplifies Heat Sinking

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Programmable Current Limit

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May Be Paralleled for Higher Current

s

Small SO-8 or PDIP Package

The LT

class AB output current in high powered amplifiers. When

connected with external transistors, the circuit becomes a

unity-gain voltage follower. The LT1166 is ideally suited

for driving power MOSFET devices because it eliminates

all quiescent current adjustments and critical transistor

matching. Multiple output stages using the LT1166 can be

paralleled to obtain higher output current.

Thermal runaway of the quiescent point is eliminated

because the bias system senses the current in each power

transistor by using a small external sense resistor. A high

speed regulator loop controls the amount of drive applied

to each power device. The LT1166 can be biased from a pair

of resistors or current sources and because it operates on the

drive voltage to the output transistors, it operates on any

supply voltage.

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Biasing Power MOSFETs

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High Voltage Amplifiers

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Shaker Table Amplifiers

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Audio Power Amplifiers

Unity Gain Buffer Amp Driving 1

Ω Load

INPUT

OUTPUT

0V

0V

, LTC and LT are registered trademarks of Linear Technology Corporation.

7

3

6

+

–

LT1166

1

µF

1

µF

1k

1k

R3

100

Ω

–

0.33

Ω

+

0.33

Ω

1

Ω

300pF

R2

100

Ω

300pF

IRF9530

IRF530

2N2222

R4

100

Ω

47

Ω

MPS2222

220

µF

2N2907

R1

100

Ω

MPS2907

+

220

µF

15V

–15V

5.6k

4.3k

2

1166 • F01

5

8

47

Ω

Figure 1. Unity Gain Buffer with Current Limit

1166 • TA01