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how to use a transistor instead of relay to drive 5v 2amps

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abhignans

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hello everyone

i am trying to power a circuit using attiny85 and tsop taking input through ir remote

the circuit consumes 5v and 2 amps
currently i am driving it using a 5volt relay.
i want to drive the circuit using a transistor
i am confused which transistor to use instead of the relay

thanks in advance for any suggestions.
 

Use BJT or MOSFET with a max output current rating of 4A to 8A. If BJT then you can use TIP series. You can also use 4 or 6A thyristor.
 

thanks for the speedy reply rajik
i have tried it using a mosfet irf540
but there is a voltage drop from 5.5 to 4.6 which makes the circuit failure
i need a bjt or mosfet with low or nill voltage drop
can u please suggest me one
 

You need to drive the transistor to saturation, in order to minimize its On-resistance, and thus minimize the voltage drop.

If you find your microcontroller cannot provide sufficient bias current to turn it on fully, then it will need more bias (more current gain). A darlington arrangement can help to boost gain.

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The 2N3055 is a common NPN power transistor, designed to handle several amperes. Its On-resistance is very low. It probably will not heat up much in your application. If it does then add heatsinking.

If you use a mosfet, then you must choose one which is designed to turn on fully when 5V bias is applied.
 

IRF540 is not a 5V compatible MOSFET. It will show a high internal resistance if the gate voltage is below, say 6V or so. It is intended to be used wit a 10V gate signal. Since you want a voltage drop of less than 1V, you have two options.

1. Trench type MOSFET (4.5V compatible)
2. Low saturation BJT
 

As milan.rajik said you can use tip series.e.g, tip41.i think it will be sufficiant for 2A.
 

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