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

[abhignans]

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.

 

[milan.rajik]

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.

 

[abhignans]

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

 

[BradtheRad]

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.

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.

 

[mrinalmani]

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

 

[hamid159]

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