Extremely low Vce(sat) transistor

S

Speakerguy

Active Member

• Jun 4, 2007

• #1

Hey,

I'm looking for a transistor with a ridiculously low Vce(sat) if possible. It needs to supply 250ma to a load, and will be driven by an output pin of a PIC (so 15-20ma drive current available I guess).

Any help is appreciated!

 

audioguru

Well-Known Member

Most Helpful Member

• Jun 4, 2007

• #2

A logic level power Mosfet will have an extremely low saturation voltage when the current is only 250mA.
For example, An IRF3711 has a typical saturation voltage of only 1.5mV when its gate voltage is only 4.5V and will be lower when the pic drives its gate up to 5.0V.

 

S

Speakerguy

Active Member

• Jun 4, 2007

• #3

I can't use a MOSFET here due to 3V operating voltage on the PIC, and needing to generate 1V across a load with an H-bridge. Which, on the top side of the h-bridge, only gives me 2V for a gate voltage I'm not experienced with transistors (I always use fet's for switches) so I didn't know how low Vce(sat) can get on nice parts, but since turn-on voltage is .7 or 1.4V I was thinking they might be an alternative.

 

Hero999

Banned

• Jun 4, 2007

• #4

Use a voltage doubler for the gate drive circuit?

You should use a bootstrap capacitor for the high side anyway.

 

Optikon

New Member

• Jun 4, 2007

• #5

Zetex has some low saturation bipolars in the range of 250mA.. also you said you can't use a mosfet but you can buy low logic level fets with 1.8V VGS(th) maximum.

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Jun 4, 2007

• #6

speakerguy79 said:

Hey,

I'm looking for a transistor with a ridiculously low Vce(sat) if possible. It needs to supply 250ma to a load, and will be driven by an output pin of a PIC (so 15-20ma drive current available I guess).

Click to expand...

It really sounds like almost any small transistor will do - but you don't actually mention what it's for, or why you think you need a "ridiculously low Vce(sat)".

 

J

j.p.bill

New Member

• Jun 4, 2007

• #7

You can find logic-level FETs with on resistances of .0004 ohm.