Power Output Stage Automatic Bias System

The LT1166 is a bias generating system for controlling 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.

Applications

* Biasing Power MOSFETs

* High Voltage Amplifiers

* Shaker Table Amplifiers

* Audio Power Amplifiers

* Set Class AB Bias Currents

* Eliminates Adjustments

* Eliminates Thermal Runaway of IQ

* Corrects for Device Mismatch

* Simplifies Heat Sinking

* Programmable Current Limit

* May Be Paralleled for Higher Current

* Small SO-8 or PDIP Package paralleled to obtain higher output current.