View bf991 datasheet:

DISCRETE SEMICONDUCTORS DATA SHEET BF991 N-channel dual-gate MOS-FET April 1991 Product specification File under Discrete Semiconductors, SC07 Philips Semiconductors Product specification N-channel dual-gate MOS-FET BF991 FEATURES DESCRIPTION • Protected against excessive input voltage surges by Depletion type field-effect transistor in a plastic SOT143 integrated back-to-back diodes between gates microminiature package with interconnected source and source. and substrate. APPLICATIONS handbook, halfpage d • VHF applications such as: 4 3 – VHF television tuners and FM tuners g2 – Professional communication equipment. g1 PINNING PIN SYMBOL DESCRIPTION 1 2 s,b 1 s, b source Top view MAM039 2 d drain 3g2 gate 2 Marking code: M91. 4g1 gate 1 Fig.1 Simplified o