What are the inputs required for amplifier design?

[deeptimongia]

hi all...
what are the inputs that i require for an amplifier design...
like s-parameters at desired bias, desired gain etc...
what are all???

in short, i wanna know about the basics of amplifier design...
can anybody help??

thanks ..

 

[dkace]

Re: amplifier design

For beginning to understand Operational Amplifiers note the following:

1. Ask your self: What does an OPAMP do?
It amplifies Voltage, current, detects the difference between two voltages, buffers a critical stage of a cicuit creating low resistance on the output and a million other things connected to the above.

2. What is my real application? Why do I want an OPAMP? For amplifying current or Voltage ? for something else?

Now here is where you need to experiment-read-ask-experiment again and so on.

So I can answer only to the basic model since I have no other info...

Two BJTs. Inputs are applied to the Bases. Emmiters are connected together and they are drived by a resistor that is connected to Vee. Collectors are separated, connected to two resistors of the same value, and resistors are connected to Vcc. From one of the collectors I take the output which is the difference of the two inputs in voltage and - after doing the math- the amplification of the current.

Where is my BIAS on the OPAMP? The resistor connected to the Emitters is the BIAS circuit which denotes the current that will pass through the BJTs and the BIAS voltage of the BJT.

The resistors on the collectors are the passive load that will determine the output voltage / current.

These are the basics in a few sentances. Now try them in a Spice algorithm, do the math and go on two a two stage OPAMP that will have an extra buffering unit on the out put? Why? You tell me after you try it. Does it need BIASing? Everything does in order to operate at the correct point.

D.

 

[deeptimongia]

Re: amplifier design

hi dkace...

u talked about OPAMP..but i need to design an amp using FET's...
i am sorry for not mentioning that...

 

[khouly]

amplifier design

is it RF amplifier , or just analog amplifier like cascode or common source

khouly

 

[deeptimongia]

Re: amplifier design

an RF amplifier..

 

[Manjunatha_hv]

Re: amplifier design

Hello Deeptimongia,

Case 1
If you want to design RF Low Noise Amplifier (LNA) then
S-parameters with Noise data is sufficient at desired bias conditions...
If you have Nonlinear Spice model it will be good for designing & analysis...

Case 2
If you want to design RF Power Amplifier (PA) then
you need to have a good Nonlinear Spice model for design & analysis.....


---manju---

 

[dkace]

Re: amplifier design

Hi ( again),

My point was to go from generic to specific!

If you know the basics about OPAMPS and you feel confident then try to move to FET differential pair and start from scratch.

What if is an LNA or PA or whatever. The basics are the same. Once you have konquered that then you need an extra 10% of effort to design your own LNA.

D.

 

[deeptimongia]

Re: amplifier design

oh !! that was ur point...u were talking in generic terms..

thanks !!