|RE:Need opinions on Q16 possible replacement (Linuxguru, Turbo3 or anyone). (modified 0 times) ||Linuxguru|
|Gate threshold voltage: My guess is that 2-4 volts is too high. In this configuration, Q16 is used as a source follower, so the source is already at a voltage of +2.0 v (or whatever value of Vcore has been chosen). Add 4 to this, and the gate voltage has to be in the neighbourhood of 6.0 v. Depending on where U16 is derives its supply voltage from, this may be too high. There has to be sufficient margin above this to allow op-amp U16 to control the current Ids through Q16 (higher currents demand larger values of Vgs).|
To summarize: stick with the existing FET(s), 6030 and 28N03, or find one with similar transfer characteristics.