741 as non inverting amp - help needed

[hameeds01]

741 as non inverting amp

whatz the minimum required supply voltage for LM741 ??
i need a simple non inverting amplifier with Gain 5, whatz wrong with my circuit y its not working ??

 

[karesz]

741 as non inverting amp

Hi,
Separate pin 4 from GND and connect it to -15V!
K.

 

[hameeds01]

Re: 741 as non inverting amp

i tried it still its not working man

 

[keith1200rs]

741 as non inverting amp

Your problem was probably caused by the fact that the 741 inputs cannot work at the negative rail (pin 4) - it needs to be 2V to 3V from the rails at least. Now that you have moved pin 4 to -15V, you also need to move the 0V end of RV1 to -15V. Be careful - you only have a 1K resistor for RV1 - it will disspiapte 0.9W which is probably too much. Use a larger value pot - e.g. 10k. I would suggest you increase the other resistors as well - the 741 will struggle to drive them.

Keith.

 

[hameeds01]

Re: 741 as non inverting amp

Gain = (1 + R2 / R1)
Gain = 5

 

[FvM]

741 as non inverting amp

Either the wiring is different from the schematic or the OP is defective.

 

[keith1200rs]

741 as non inverting amp

Have you built this, or is it a simulation?

Keith.

 

[hameeds01]

Re: 741 as non inverting amp

it is just a simulation i'm wondering y its happening so ,

my design Requirements are::

i/p: 0-->1v , o/p: 0-->5v , o/p current: 15mA
Available supply voltages: 5v , 8v

now tell me guys what should i do ??

 

[FvM]

Re: 741 as non inverting amp

Thanks Keith.

A net connector with the designator "-15" doesn't necessarily imply a voltage source connected to it.

In a simulation, you have all means to check node voltages and even internal 741 nodes. Don't ask "why my circuit is not working"
unless you have inspected at least the external voltages and currents. If you don't understand the results, you can present them at
edaboard.

Personally, I prefer to hear the word simulation circuit related to this stuff.

 

[hameeds01]

Re: 741 as non inverting amp

now its working with gain 5,
but is there any away to operate it without -ve supply i mean instead of that can we use Gnd ??

 

[karesz]

Re: 741 as non inverting amp

...you also need to move the 0V end of RV1 to -15V. ...it will disspiapte 0.9W...

Hi Keith,
Sorry, but if hes spec is Uin=0...+1V_nobody does a poti to U- as reference potential.
He connected to the poti +5V (only), also it has had from begining only 25mW (5mA)to dissipate...
I agree, it can be_in these circuit version_ higher value, i.e. 10K Ohm too.
K.

 

[keith1200rs]

Re: 741 as non inverting amp

...you also need to move the 0V end of RV1 to -15V. ...it will disspiapte 0.9W...

Hi Keith,
Sorry, but if hes spec is Uin=0...+1V_nobody does a poti to U- as reference potential.
He connected to the poti +5V (only), also it has had from begining only 25mW (5mA)to dissipate...
I agree, it can be_in these circuit version_ higher value, i.e. 10K Ohm too.
K.

Sorry, I didn't spot that- I assumed it was to the +15V.

Now I know it is a simulation it is easier to fix (and it seems he has).

It should work without the -15V but not when the input is 0V with a 741. A more modern opamp would be a better choice. Even the old LM324 will work with inputs at the negative rail.

Keith.