Dear Friends:

I am trying to design a feedback amplifier with closed loop gain of 10 (amplifier can be V/V, V/A, A/V or A/A) using Ye Olde 741 and a BJT or FET.

Can you share any general suggestions or recommendations? I have looked into a transconductance amplifier which was designed for 1mA/V, but I don't believe it can be simply "ported" to 10 A/V...I have also looked into the "FET Circuit Applications" (National Semiconductor, App. Note 32, 1970) at the "electronic gain control" circuit, but I'm not sure about its implementation with the 741...I am trying to go for as few parts as possible, using "ideally" just a 741, BJT/FET and resistor...Thanks for your help and I look forward to your thoughts!

 

What do you want to amplify?

 

You might find this useful - http://www.allaboutcircuits.com/vol_3/chpt_8/5.html

Why do you need a transistor in addition to the 741?

 

Oops - apologies for the confusion - I do not need to use ye olde 741 after all!

Instead I have decided to use the voltage amplifier attached below. Now my question is, how should I choose the FET if I want to achieve a gain of 10V/V?

mik3: I just want this to be a "shunt shunt" feedback voltage amplifier, it is generically a single-stage amplifier.

Thanks for your help!

 

Replace the FET with its π-model and find how the gain is determined.