#2n3055 transistor rf amplifier how to
#2n3055 transistor rf amplifier install

Moreover since the collectors of the transistors are supposed to be in parallel and joined with each other, the use of mica isolators no longer become essential and makes things much convenient as the body of the transistors get connected in parallel through their heatsink metal itself. Mounting over a common heatsink will ensure quick and uniform sharing of heat and eliminating the dreaded thermal runaway situation. This idea will allow you to get rid of the messy wire-wound emitter resistors.

#2n3055 transistor rf amplifier how to

Rb = 11.3 x 50 / 3 = 188 Ohms How to Avoid Emitter Resistors in Parallel BJTsДЄlthough the use of emitter current limiter resistors looks good and technically correct, a simpler and a smarter approach could be to mount the BJTs over a common heatsink with a lot of heatsink paste applied to their contact surfaces. Let's assuming hFE = 50, Load current = 3 amps, the above formula could be solved as under: Rb = (12 - 0.7)hFE / Collector Current (Ic) When two or more transistors are connected in parallel, due to their slightly differing individual characteristics (hFE), the transistors in the group may dissipate at different rates, some a little faster and others a little slower.Д¬onsequently, the transistor which may be conducting slightly more current through it might start getting heated up faster than the neighboring devices, and soon we may find the device entering into a thermal runawayВ situation damaging itself and subsequently transferring the phenomenon to the remaining devices as well, in the process. ThisВ situationВ is called thermal runaway, in transistors. The process gets into a kind of chain reaction heating the device rapidly until the device becomes too hot to sustain and gets permanently damaged. Moreover, BJTs have a negative temperature coefficient characteristic which force them to increase their rate of conduction proportionately as their case temperature increases.ДЄs its case temperature tends to increase, the current through the transistor also increases, which forces the device to heat up further.

#2n3055 transistor rf amplifier install

And that's why we install heatsinks on them to maintain the aboveВ criterion. What is 'Thermal Runaway' in BJTsДЄs per their specs, transistors (BJTs) need to be operated under reasonably cooler conditions, so that their power dissipation does not exceed the maximum specified value. Though using single BJTs is relatively easier, connecting them in parallel needs some attention due to the one significant drawback with transistor characteristics. Therefore it becomesВ necessaryВ to connect theses devices in parallel. Normally, single BJTs become sufficient for getting moderate output current, however when higher output current is required, it becomes necessary to add more number of these devices together. These stages primarily may consist of power devices like the power BJTs or MOSFETs. This usually is not possible using single transistors, and requires many of them to be connected in parallel.

This involves creating a power stage that can handle high power with least effort. While making power electronic circuits, configuring the power output stage correctly becomes very crucial. In this post we will learn how to safely connect multiple transistors in parallel, these can be BJTs or mosfets, we will discuss both.