+V, -V supply from 9V battery to power LM741

[Slik_Willie]

I am designing a circuit that include a LM741 as comparator that requires +Vcc -VEE from a 9V battery. Can this be accomplished using voltage divider? If so. How? If not, your suggestion.

[Audioguru]

Any opamp can be biased at half the supply voltage then use a single polarity supply.
But some 741 opamps do not work with a supply voltage as low as only 9V.

[beenthere]

All the data sheets characterize the 741 for operation at +/-15 VDC, and never for single supply. If the 741 is an anemic op amp, it is a really bad comparator. Don't know what your inputs might be, but an LM311 would offer superior operation (it is a comparator).

[Nanophotonics]

I'm currently using the LM324 for my single supply applications.

[Audioguru]

Originally Posted by Nanophotonics

I'm currently using the LM324 for my single supply applications.

It is extremely slow. Its output has slew-rate limiting at only 2kHz and higher. Higher frequencies become triangle-waves with reduced level. The gain is only 12 at 40kHz. It has 3% crossover distortion because its output transistors have no bias current for low power. It is noisy.

The MC33171 single, MC33172 dual and MC33174 quad opamps have exactly the same low power but have no crossover distortion, also operate from a supply as low as 3V and have a full output up to 35kHz. Their gain is nearly 40 at 40kHz. Their inputs work at the negative supply voltage that could be 0V. Their outputs go down very close to the negative supply voltage that could be 0V. But their output high current is only 3mA to 5mA.

The MC34071 single, MC34072 dual and MC34074 quad opamps also work from a single supply as low as 3V and their inputs and outputs work down to 0V. They have normal supply and output currents and a full output up to 100kHz.

[Nanophotonics]

Thanks for the explanation. You're the guru, so I leave it to the more knowledgeable.

[Slik_Willie]

Thanks for the tip Guru.

[BMorse]

Originally Posted by Slik_Willie

I am designing a circuit that include a LM741 as comparator that requires +Vcc -VEE from a 9V battery. Can this be accomplished using voltage divider? If so. How? If not, your suggestion.

to answer your question, yes there is a way you can get the +VCC and -VEE from 2 9 volt batteries to power a 741 opamp...




B. Morse

[buckysparks]

Here is a simple way of generating +/- supply with a catalog coupled inductor and a integrated switching regulator.

http://focus.ti.com/general/docs/lit...Number=slva369

[t_n_k]

Another possible way of doing it using a 1/4 of LM324. Apologies to those who would love to see the back of LM324's.