Need OP AMP - Electronic Circuits Projects Diagrams Free

PedroPT · 10th July 2005, 06:19 PM

Hi,

I'm using 741 in a project but it has such output resistance that it interfeers with the next stage.

I need to know the reference of a similar OP AMP with a much lower output resistance.

Could you give me advice on this one?

P.S. The op amp is just doing a buffer stage.

**Jay.slovak** · 10th July 2005, 06:50 PM

Try LM358 (LM258 LM2902...), it's rail-to-rail OpAmp, ideal for buffering.

**Nigel Goodwin** · 10th July 2005, 07:01 PM

You might also mention what the input impedance of the following stage is?, it's rather relevent to the question.

Presumably it must be pretty low?, in order to cause problems.

But really, there's no reason to be using a 741 in the 21st century, in their day they were a decent little amp, but their day was many decades ago! - you can get FAR better amps for very little cost, in fact it's probably difficult to buy a worse opamp than a 741?.

**Jay.slovak** · 10th July 2005, 07:14 PM

Yes, 741 is pretty old, and has few problems (eg output can't go rail-to rail), but people still use it beacuse it's included in many designs...

PedroPT · 10th July 2005, 08:26 PM

ok. I',ll try that one!

The input impedance is a 12 volt lamp. I really don't know what it measures in Ohms because I don't have the lamp here with me. But I guess you, who have a lot more knowledge in electronics than I, must have an ideia.

The lamp is used has a "reading" light inside a car. The project was just a simple, delay-adjustable, fade out.

Thanks once again.

**Jay.slovak** · 10th July 2005, 09:25 PM

Uff, why didn't you tell us before that you want to drive big load? In this case, simple emiter folower with NPN transistor would to the job. OpAmps are good for driving small loads, with NPN you can drive huge many Amps loads.

Sebi · 10th July 2005, 09:27 PM

Huh, a lamp? Not wonder... You need a power transistor or FET for lamp driving from opamp output!

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10th July 2005, 06:19 PM	(permalink)
PedroPT	Need OP AMP Hi, I'm using 741 in a project but it has such output resistance that it interfeers with the next stage. I need to know the reference of a similar OP AMP with a much lower output resistance. Could you give me advice on this one? P.S. The op amp is just doing a buffer stage.

10th July 2005, 06:50 PM	(permalink)
Jay.slovak	Try LM358 (LM258 LM2902...), it's rail-to-rail OpAmp, ideal for buffering. __________________ "I share, thus I am" Jay.slovak Read this! ICD2 Clone Best PIC/DsPIC Bootloader Read my Inchworm ICD2 review!

10th July 2005, 07:01 PM	(permalink)
Nigel Goodwin	You might also mention what the input impedance of the following stage is?, it's rather relevent to the question. Presumably it must be pretty low?, in order to cause problems. But really, there's no reason to be using a 741 in the 21st century, in their day they were a decent little amp, but their day was many decades ago! - you can get FAR better amps for very little cost, in fact it's probably difficult to buy a worse opamp than a 741?. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

10th July 2005, 07:14 PM	(permalink)
Jay.slovak	Yes, 741 is pretty old, and has few problems (eg output can't go rail-to rail), but people still use it beacuse it's included in many designs... __________________ "I share, thus I am" Jay.slovak Read this! ICD2 Clone Best PIC/DsPIC Bootloader Read my Inchworm ICD2 review!

10th July 2005, 08:26 PM	(permalink)
PedroPT	thx ok. I',ll try that one! The input impedance is a 12 volt lamp. I really don't know what it measures in Ohms because I don't have the lamp here with me. But I guess you, who have a lot more knowledge in electronics than I, must have an ideia. The lamp is used has a "reading" light inside a car. The project was just a simple, delay-adjustable, fade out. Thanks once again.

10th July 2005, 09:25 PM	(permalink)
Jay.slovak	Uff, why didn't you tell us before that you want to drive big load? In this case, simple emiter folower with NPN transistor would to the job. OpAmps are good for driving small loads, with NPN you can drive huge many Amps loads. __________________ "I share, thus I am" Jay.slovak Read this! ICD2 Clone Best PIC/DsPIC Bootloader Read my Inchworm ICD2 review!

10th July 2005, 09:27 PM	(permalink)
Sebi	Huh, a lamp? Not wonder... You need a power transistor or FET for lamp driving from opamp output!