One of the most frequent uses of n-channel MOSFET’s is as a voltage
controlled switch. To ensure that the MOSFET delivers the full supply
voltage to the load it is necessary for the gate voltage to be a few
volts above the supply voltage level. This can be a problem if no other
suitable higher volt-age sources are available for use elsewhere in the
circuit. The LTC 1982 dual high-side switch controller from Lin-ear
Technology (www.linear-tech.com) solves this problem by incorporating a
voltage tripler circuit in the gate driver stage.
Dual High Side Switch Controller Circuit Diagram
The gate voltage is limited to +7.5 V which is 2.0 V above the IC’s maximum operating voltage. It can directly drive the gate of logic-level MOSFET with a VGS(th) from 1.0 V to 2.0 V. A suitable n-channel logic level MOSFET would be the BSP 295. This device can switch up to 1.5 A and is available in an SOT 233 SMD package.
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