Help with Discrete Op-Amp

[refreshzone]

Hey guys
I need some help to get started on making a Discrete Op amp which has following capabilities:



Only discrete devices (BJT, FET, TUBES) may be used.

Capable of driving a 50 K ohm load to + 10 V

Frequency response DC - 10MHz + 2 db.

The input impedance must be at least 1 Megohm

The output impedance must be less than 50 ohms

This amplifier will be packaged in such a way that it does not exceed more than 3 inches on any side.

The gain must be between 1000 - 1500

 

[dougy83]

Hey guys
I need some help to get started on making a Discrete Op amp which has following capabilities:

Have a look here (first result from googling "discrete opamp"): **broken link removed**. You might want to use it as a base design.

Also have a look at the datasheet for a transistor opamp e.g. LM358. The basic circuit is shown, which can be used as a base.

Capable of driving a 50 K ohm load to + 10 V

controlled by supply voltage and amp output impedance.

The input impedance must be at least 1 Megohm

Can use fets or darlington pairs to increase the input impedance.

The output impedance must be less than 50 ohms

use appropriately small resistors in the stages leading up to the output drivers

The gain must be between 1000 - 1500

Open-loop gain? Closed loop gain? usually you want the gain of the opamp to be as high as practicable; the closed-loop gain is then adjusted with feedback resistors.

 

[Torben]

Also check out the book "Art of Electonics" by Horowitz & Hill. It has an excellent section on op-amps and includes the basics needed to build one from discrete components. I also agree with dougy's note that you can get the equivalent schematic from many op-amp datasheets, and as dougy said, the LM358 is a nice simple one to start with.


Torben