Another design that uses the output
transistor technology V-MOSFET. The transistors are we offer many
advantages over a simple bipolar transistor, such as high speed,
thermal stability, low distortion, etc.
use of diodes D2 until D5 in combination with the resistances R17-19,
they protect the gates of transistors v-fet from exceeds the voltage ±
14V and it creates perforation in very thin layer SiO2, that is used as
insulation in the gate. This way of protection is common in all the
amplifiers that use these transistors. The total gain of amplifier is
32.6, regulated from the R18, R6 and R8, in the negative feedback. Also
is used enough the use of local feedback for stabilisation of operation
under all the conditions. Because the transistors v-fet have positive
factor of temperature, with result with the increase of temperature is
increased also their resistance. This increase has as result the
reduction of current that via the transistor, hence also his power. The
use of separated supply in the stages of drive and exit, ensures
stability and reject of distortion of intermodulation.
VMOS FET POWER [ 2SK134 or 2SK135 ] [ 2SJ49 or 2SJ50 ], they are that,
more above transistor they are not produced more by the Toshiba and are
enough difficult they are found henceforth. They can be replaced with [
2SK1530 in the place of 2SK135 ] and [ 2SJ201 in the place of 2SJ50 ].
The new transistors are in plastic case ΤΟ-3Ρ and no TO-3, bear in
bigger supply of operation and have positive factor of temperature.
This mean that with the increase of temperature, is increased and the
current that is gone through from through the transistor. The new
transistors him I have still not tryed and me it would interest to
learn if somebody him used also with which results.