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Low voltage FET for 1.5V battery application

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I'm looking for a transistor to be used as a switch in a 1.5V battery application. The load is a small motor that requires 400mA start current and 200mA full load current. I would prefer a through hole device.

Searching Digi-Key the best candidate appears to be SSM3K56FS (this is actually a SMT device) https://www.digikey.ca/product-detail/en/SSM3K56FS,LF(T/SSM3K56FSLF(TCT-ND/3863601

Can anyone make a better suggestion?
 

Considering the expectable Vgsth variation and battery voltage drop (should work down to 1.2 or even 1.0 V, I presume), MOSFET isn't a reasonable option (unless you are adding some kind of boost converter for the gate voltage). BJT switch seems a lot easier, although involving a slightly higher voltage drop and base current losses.
 

FvM said:
Considering the expectable Vgsth variation and battery voltage drop (should work down to 1.2 or even 1.0 V, I presume), MOSFET isn't a reasonable option (unless you are adding some kind of boost converter for the gate voltage). BJT switch seems a lot easier, although involving a slightly higher voltage drop and base current losses.
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Do you think this is a good candidate? https://www.digikey.ca/product-detail/en/ZTX549/ZTX549-ND/92540
 

Well suited for your application, I think, with sufficient current gain at 400 mA.
 
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R3 must have lower resistance value. Should be chosen for forced Beta 20-50 at lowest battery voltage.
 
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For low voltages and large currents, try a reed relay offering a contact resistance of 0.01 Ohm at any voltage level.
 

FvM,

Thanks for your input, always appreciated. I will build and test it.

I still owe you an answer to one of the op amp questions I posted, I have been too busy to ponder your question, but I will.

Regards,
 


Re the FPF1015, I don't understand the ON input Voltage specification Von(min) 1.8 to 4.0V?
Click to expand...
Whatever the device exactly does, it's apparently not suited for 1.0 to 1.5 V single supply.

- - - Updated - - -

I also noticed that Vishay has a series of MOSFETs with "1.2V VGS rated rdson", which is a step towards allowing a single FET switch.
 
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FvM said:
Whatever the device exactly does, it's apparently not suited for 1.0 to 1.5 V single supply.

- - - Updated - - -

I also noticed that Vishay has a series of MOSFETs with "1.2V VGS rated rdson", which is a step towards allowing a single FET switch.
Click to expand...

No, apparently not.

This is a p-fet candidate:
https://www.onsemi.com/pub_link/Collateral/MCH3383-D.PDF

Rated at 0.9V although Rdson is bad at 0.5 ohms, but at 1.2V it's 0.17 ohms worst case.
 
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