Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

How do you get big amplification on an NMOS?

Status
Not open for further replies.
A

Addez

Newbie level 6
Joined
Jun 9, 2011
Messages
12
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,397
In school they teach us how to calculate on NMOS circuits, but we never learned the basics for how to design your own circuit.
I know how to give a bias voltage on the gate. This leads to a current on the drain, which leads to a voltage across the drain and source resistor.

But I never got guidelines on how to design a circuit.
I want BIG signal amplification and drain minimum power doing so.
What resistor should I change to increase amplification?
I'm guessing the drain resistor but I'm getting nonsense readings from LT-spice when I do that.

Please help me I'm getting nervous breakdown over this.
 

The transconductance of a Fet is fairy low. Like any transistor it can have a high voltage gain if its drain resistor is a current source instead and its load has a high impedance. The current source should produce the same DC current as a resistor.
 

How do I make the drain resistor a current source?
And by load resistance I believe you mean the load + drain and source resistors?
 

If you didn't learn about current source circuits then you can look in Google at some.

The load is the external load, probably capacitor-coupled. For high voltage gain you do not use a drain resistor, instead you use a current source that has a very high impedance. You might not need a source resistor unless it is a depletion mode Jfet.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top