# How to simple control output voltage of 9v battery - from 0 to 9?

#### UnnamedUser159

Joined May 3, 2016
501
I want to define the output voltage of the battery to give the nessesary voltage to mosfet x and y, exactly how much it needs./for testing purpose/

You can use simple Paint to show me.

thanks

Joined Feb 20, 2016
3,564
Try just wiring a 10K pot across the battery.

#### UnnamedUser159

Joined May 3, 2016
501
could you show me the connections?

i think like that. connecting just basic resistance to the + just decrease the current but the voltage stays the same. If i connect that pot just on the + wire it will just regulate the current...

#### Alec_t

Joined Sep 17, 2013
11,398
I want to define the output voltage of the battery to give the nessesary voltage to mosfet x and y, exactly how much it needs./for testing purpose/
Voltage is one thing, current is something else. What tests will you do and how much current will you need to draw? A simple potentiometer can set a voltage but can't pass much current.

#### abraar_sameer

Joined May 29, 2017
37
You can use a linear adjustable voltage regulator, like an LM317. That won't give a complete 0-9v range though. Maybe you will get upto 7 or 8V. The circuit is pretty simple. Look up its datasheet for more details.

#### jpanhalt

Joined Jan 18, 2008
9,705
I want to define the output voltage of the battery to give the nessesary voltage to mosfet x and y, exactly how much it needs./for testing purpose/

You can use simple Paint to show me.

thanks
This question is reminiscent of how to test whether a mosfet works. For ordinary N-channel mosfets, 9V between gate and source will be fine. If that makes you uncomfortable, put a resistor (100 ohm) in series.

If you want to know the threshold voltage, that information is in the datasheet. If you want to measure other characteristics, test rigs for doing that are often in the datasheets. If not for your specific device, look at another device.

#### DickCappels

Joined Aug 21, 2008
6,457

This is what dendad mentioned in post #2. It is fine for biasing the gate of a MOSFET.

For a variable positive voltage use the - battery connection as a reference and take the adjustable output from the wiper.

For a variable negaitive voltage use the + battery connection as a reference and take the adjustable output from the wiper.

#### UnnamedUser159

Joined May 3, 2016
501
Yep. i went to store and took LM317 2pcs.

the idea is me to have this advanced tester from http://www.4qdtec.com/mostest.html and to be able to test most of the mosfets used nowadays.

if the 9v battery with Resistance is :
enought to do the job
wont damage the mosfet
its good option for me. is it ?