hi friends
i am trying to design an amplifier for 7v output and 11ma current, using ua741 ic using non-inverting amplifier. i am not able to get current as 11ma i am getting voltage twice the input voltage i was not getting an current 11ma,pls help me i used Rf=1kohm and Rin=1kohm and input voltage 3.5v and supply voltage 12v help me?
Thanks
I understand you made a non-inverting opamp circuit with a gain of two.
And you are getting 7volt out with 3.5volt input.
What I don't understand is the "current" part.
What "load" is using, or has to use 11mA.
Leo..
I am not using load resistance here,ok how much should i use a load resistance for this to get 11ma.
What do you want this amplifier to power?
What is its input impedance?
Why the current specification?
Why use such a very old op amp?
Please post your schematic.
rahulsubbu:
I am not using load resistance here,ok how much should i use a load resistance for this to get 11ma.
Resistance = 7 V / 11 mA = 636 ohms.
Russell.
ok then help me which amplifier should i use..russel If i use load resistance current is decreasing than the previous.
Show us your schematic. How are you measuring the current if not in a load?
Russell.
russellz:
Show us your schematic. How are you measuring the current if not in a load?how to upload schematic here.
http://www.instructables.com/id/Non-inverting-amplifier-with-uA741/?ALLSTEPS
this the link which i followed
Because i want to activate relay,relay requires 11ma current.
Now we are getting somewhere. You don't want an amplifier circuit. You want a switching circuit. See this for example: http://playground.arduino.cc/uploads/Learning/relays.pdf
Russell.
Thanks russel, but i am not using arduino i am giving input from proximity sensor directly to amplifier.
rahulsubbu:
Thanks russel, but i am not using arduino i am giving input from proximity sensor directly to amplifier.
The same applies.
Follow the link that russellz posted and you will be fine!
// Per.
The '741 was the first mass-market opamp back in the 1960's - its half a century old.
You would do best to find a rail-to-rail opamp capable of running at 5V upto 20V or so, get
a couple as they will be handy for other projects, or as a spare if you goof it up.
The LM358 will handle inputs and outputs down to the negative rail (GND), and will be OK
for 7V signals from a 12V supply. There are true rail-to-rail devices though that can handle
the full supply range. Watch out for some of these modern opamps only cope with supplies
upto 6V or so. The LM358 handles supplies from 3 to 32V though, so it ought be good for
this application, it should handle 11mA.
This is the perennial XY problem.
rahulsubbu needs to answer Mike's questions. He needs to explain what he is trying to do, not to randomly choose circuits which he clearly does not understand.
This is clearly not a discussion of op-amps.