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When do you need a parallel circuit with a BJT?
For an application where you need to parallel transistors and control current in a linear fashion (not switching the transistors fully on and off), BJTs are your best bet. As Olin Lathrop says, the circuit will need to have resistors in series with the BJT emitters to help balance current.
How are bipolar transistors connected in parallel Tech Tips?
Bipolar Transistors connected in parallel. Bipolar Transistors (BJTs) can be connected in parallel if balancing resistors are placed in series with the emitter. BJTs generally tend to become more conductive as their temperature increases.
Which is worse paralleled FETs or BJTs?
So, current imbalance between paralleled FETs in linear operation will be much worse than BJTs (and they are bad enough). To linearly control current with a MOSFET, V gs needs to be actively controlled by a feedback loop. Here is a recent example of what happens when the MOSFET is not controlled by the feedback loop.
Are there any linear regulators that are easy to parallel?
The devices are easy to parallel and share current very well. They positive output regulators have an input voltage range up to 40V and provide output currents from 0.2A to 3A. A simplified diagram of the LT3081 is shown below.
Why are parallel parallel transistors more reliably operated?
Typically, BJTs can be more reliably operated in parallel if balancing resistors are placed in series with the emitter, rather than the base. Even a small resistance here will strongly counteract the tendency for imbalance, because an increase in current flowing through any one transistor causes the applied base-emitter voltage to decrease.
How are resistors tied together in bipolar transistors?
The simplest way to get around this with bipolar transistors is to put a small separate resistor in series with each emitter. You have a 50 Ω Load, so 1 Ω emitter resistors should be fine. Now you tie all the bases together direction.
Do you need a base resistor for a BJT?
On the schematics are shown 2 diodes, but that will be expanded to 8 LEDs for each shift register. The base resistors R3 and R4 are doing nothing useful. The circuit would be better with them replaced by wires.