Hello,

I was wondering if someone could help. I need an inverting op-amp using a 741. I needs an input impedance of 200 - 2k Ohms and a voltage gain of 6-40 at a frequency of 200Hz-5Khz when loaded with its characteristic output impedance.

Any help would be greatly appreciated!

Thanks

 

something along this design is this what your after?

http://www.rason.org/Projects/opamps/opamps.htm

 

Hello,

I was wondering if someone could help. I need an inverting op-amp using a 741. I needs an input impedance of 200 - 2k Ohms and a voltage gain of 6-40 at a frequency of 200Hz-5Khz when loaded with its characteristic output impedance.

Op amps don't really have a "characteristic output impedance", just a maximum output current they can drive. Is that what you mean?

 

something along this design is this what your after?

http://www.rason.org/Projects/opamps/opamps.htm

Something like that, yes. I know how to figure the gain. What I am getting stuck on is the input and output impedance. I need the input impedance to be between 200-2k ohms, then I need to measure the output impedance.

 

Really, I am having trouble with the input and output impedance. I need an input impedance of 200 - 2kohms and then I need to measure the output impedance.

 

I'm not sure what's your purpose for Input resistance of Op Amp?

Because the Input resistance is really high, but you cann't reduce it from inside, so you can do it from outside, you just need to connecting one 1KΩ resistor to the input pin and ground, then the Input resistance will be close to 1KΩ, it's value between 200Ω and 2KΩ, or you want to change it to the value you like.

See page 5.
ri, Input resistance, 25°C, 0.3 2, 0.3 2 MΩ
ro, Output resistance, VO = 0, See Note 5, 25°C, 75 75 Ω
http://www.datasheetcatalog.org/datasheet/texasinstruments/ua741.pdf

 

the input impedance is set by the resistor on pin 2, which also sets the gain, so the circuit at the bottom has an input of 1k and a gain of 100.

 

Do you mean the two resistors on pin two? This being an inverting Op amp?

 

the input impedance is set by the resistor on pin 2, which also sets the gain, so the circuit at the bottom has an input of 1k and a gain of 101.

What do you mean the circuit at the bottom?

 

The bottom of the page that was given a link in post #2

and the gain is 100. You got it mixed up with the non-inverting formula, Dave.

 

Got it! Thanks for the help.