How to choose a transistor?

Question

Electronics

For example: the task of controlling an engine from a microcontroller. If I know that the motor consumes 100mA, there are surges up to 400mA when turned on. Management - from the foot of the microcontroller to the base, then the current is 20mA. How to choose a specific transistor?

Answer 1

The chip and dip have a parametric catalog www.chipdip.ru/catalog/bipolar-transistors
The compel is even cooler www.compel.ru/catalog , although they don’t work with physicists,
bc817 will suit you, the current is a protective diode in the collector, in the base 1 kOhm is enough, the current will be, 2-4mA is enough
for inductive loads (motors, relays) the popular ULN2003 microcircuit
still has transistors for programmers :), with built-in resistors based

Answer 2

I have asked this question many times on the forums. No one could understand what I want from them. Apparently, hardened electronics engineers have a database on transistors in their heads. I save myself with this: ru.mouser.com/_/N-ax1sh
There is a selection by parameters. Then I look for the model already, where to buy.

Answer 3

Transistor as a key. Any cheapest transistor passes through the current. With a base current of 20 mA (naturally, it must be limited by a resistor), it will be fully open and the voltage drop across the CE will be tenths of a volt, and, accordingly, heat dissipation will be tenths of a watt.
In general, download Proteus, it is in the free version, there is good circuit modeling and a decent elemental base, choose something from the nearest store, and substitute it in Proteus.