Depletion mode MOSFETs, unlike the regular enhancement type MOSFETs, require a negative gate bias to turn off. Consequently, they remain on at or above zero gate bias voltage but otherwise have similar MOSFET like characteristics. They are suitable for level shifting, solid state relays, current regulators, and active loads.

Features:

• ‘Normally-On’ operation
• Linear mode tolerant
• Internal standard packages
• UL 94 V-0 Flammability qualified
• (molding epoxies)

Applications:

• Audio amplifiers
• Start-up circuits
• Protection circuits
• Ramp generators
• Current regulators
• Active loads

Product page: https://www.littelfuse.com/products/power-semiconductors/discrete-mosfets/n-channel-depletion-mode/standard_depletionmode.aspx

When Power MOSFETs are used in the linear-mode operation, as opposed to their conventional switch-mode one, they are required to endure substantially high thermal and electrical stresses due to the simultaneous occurrence of high drain voltages and currents; these extreme stresses can cause typical devices to fail. IXYS Linear MOSFETs have been designed to address these kinds of device failures – the FBSOAs are “extended” when the positive feedback of electro-thermal instability is suppressed, giving rise to larger “operating windows.” The FBSOAs are guaranteed at 75°C.

Features:

• Designed for linear operation
• Guaranteed FBSOA at 75°C
• Avalanche rated
• International standard packages
• UL 94 V-0 Flammability qualified
• (molding epoxies)

Applications:

• Current regulators
• Fan controllers
• Linear amplifiers
• Fan controllers
• Programmable loads
• Soft-start control
• Solid-state circuit breakers