Bi-directional Switching using MOSFET

Thread Starter

DirtyBits

Joined Jul 30, 2011
8
Hi there,
I am working on project which has only one line for Input and Output. Which also requires switching at load current of 500mA to 1A. Basically there are two loads 1. runs on Vin while
2. runs on battery
but both use the same wire.
I do not have much experience with MOSFET and my initial attempt is as follow ;)




Que: What would be the Output voltage Vout = Vbat - Vds?? = 5V - (Ids*Rds) or 5V - 0.7V ??
Also is there any readily available chip that can be used for this kind of application?
Please point out any flaw in the circuit and really appreciate your suggestion/advice on this matter.

Regards
 

crutschow

Joined Mar 14, 2008
34,432
First off you don't want R3 and R5. The just reduce the gate drive and which causes a higher ON resistance for the FETs.

Your math is off by an order of magnitude. The ON resistance of the MOSFET is 70mΩ so the source-drain voltage drop at 1A is 70mV not 700mV.

You circuit just requires two MOSFETs and two resistors. You can't get much simpler than that.
 
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