using a buz11 with a motor!

[icetea]

i want to learn how to bias mosfets!!!!!!

1. mosfets need voltage and no current to switch on right?

2. do they amplify current or only voltage?

3. how can i connect a buz11 as a switch to a small motor from
toys?

 

[Boncuk]

Hi icetea,

MosFets are controlled by voltage, requiring very little current (somewhere in the µA or nA range)

MosFets do not amplify. They just switch.

You can connect the motor between drain and +VS using an N-channel MosFet. Connect the source directly to ground or via a shunt resistor if you want to measure motor current to use the voltage drop across the shunt to calculate for current.

The gate voltage must be depicted of the data sheet.

A BUZ11 switches OK at a gate voltage of 3 to 5V (better go for 5V, 3V is the lower limit)

Boncuk

 

[crutschow]

MosFets do not amplify. They just switch.

Not so. Even a switch can be considered an amplifer since it's amplifying a digital signal. The output power controlled is greater than the input controlling power which is the basic definition of an amplifier.

And if you bias a MOSFET properly it will amplify an analog signal, just as a bipolar transistor can. The difference is that a MOSFET is a voltage-to-current amplifier (similar to an old pentode vacuum tube) while the bipolar transistor is a current-to-current amplifier.

But of course you can convert the output current to a voltage by running it through a resistor (which is what most voltage amplifiers do).

 

[icetea]

The gate voltage must be depicted of the data sheet.

A BUZ11 switches OK at a gate voltage of 3 to 5V (better go for 5V, 3V is the lower limit)

where exactly is that detail in the datasheet?

i'm a little confused now, a mosfet only switches or amplifies too?
i guess the value of the voltage at the gate controls the amount
of current between drain-source is that right?

can somebody give me some examples on where we need mosfets
and why?

 

[Roff]

A BUZ11 switches OK at a gate voltage of 3 to 5V (better go for 5V, 3V is the lower limit)

Boncuk

Rds(on) is only guaranteed at Vgs=10V. It is not specified at 5V. See below.