lm387 made od discrete components

neazoi · 20th January 2011, 10:49 AM

Hello This little amplifier is from a radio receiver.
I wish to replace the chip with an amplifier made of discrete components and achieving the same overal gain and maybe better noise, distortion and intermodulation characteristics.

The 120mH coil and associated caps form a high pass filter to cut off the 50Hz hum. I would like to keep this passive filter there as well as the mute switch, so I basically need 2 amplifiers made out of discrete components. One with gain 27dB for the front end and another one with gain 35dB for the back end.

Can this be done? any schematics?

jscherer · 11th September 2012, 11:46 PM

This is an old thread but I thought I would chime in too. I am building the same receiver that you were referring to in this post. I am looking for a better preamp then the LM387. Everything I read says go with the NE5534. Can I drop in a NE5534 in place of the LM387 or do I need to make some changes?

jscherer · 12th September 2012, 12:14 AM

never mind... looks like the ne5532 is a direct replacement..

Bibliophile · 12th September 2012, 01:14 AM

Just curious, which ARRL publication is that circuit from?

jscherer · 12th September 2012, 02:47 AM

Yep, its one written by Rick Cambell, KK7B - entitled "High Performance, Direct conversion Receivers." You can find it here

tomchr · 12th September 2012, 04:07 AM

For lower noise, I'd recommend the LME49710 (LME49720 for the dual).

~Tom

djQUAN · 12th September 2012, 05:49 AM

Quote:

Originally Posted by jscherer

never mind... looks like the ne5532 is a direct replacement..

No. The pinout is different and the LM387 is a unique op amp such that it is designed to work with only single supplies. The non inverting inputs are internally biased so that the output can work with single supplies without external biasing networks.

http://www.ti.com/lit/ds/snosbt7a/snosbt7a.pdf

franzm · 12th September 2012, 07:10 AM

NE542 is a direct replacement for LM387.

neazoi · 12th September 2012, 07:27 AM

Quote:

Originally Posted by franzm

NE542 is a direct replacement for LM387.

And which of the two is of lower noise?

jscherer · 12th September 2012, 10:18 PM

The NE542 is 0.7uV and the LM387 is 1.0uv so both are about the same. The LME49710 is listed as 2.5nV/Hz. So the LME49710 is it the lower noise winner which comes as no surprise. Given that bit of information, the bigger question I have is how should I go about reconfiguring the two preamps in the above circuits to use the LME49710.

12th September 2012, 04:07 AM	#6
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	For lower noise, I'd recommend the LME49710 (LME49720 for the dual). ~Tom __________________ 21st Century Maida Regulator, Universal Filament Regulator, 300B Driver PCBs, and more... Neurochrome : : Audio - http://www.neurochrome.com/audio - Engineering : : Done : : Right

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11th September 2012, 11:46 PM	#2
jscherer diyAudio Member Join Date: Apr 2008	This is an old thread but I thought I would chime in too. I am building the same receiver that you were referring to in this post. I am looking for a better preamp then the LM387. Everything I read says go with the NE5534. Can I drop in a NE5534 in place of the LM387 or do I need to make some changes?

12th September 2012, 12:14 AM	#3
jscherer diyAudio Member Join Date: Apr 2008	never mind... looks like the ne5532 is a direct replacement..

12th September 2012, 01:14 AM	#4
Bibliophile diyAudio Member Join Date: Nov 2011	Just curious, which ARRL publication is that circuit from?

12th September 2012, 02:47 AM	#5
jscherer diyAudio Member Join Date: Apr 2008	Yep, its one written by Rick Cambell, KK7B - entitled "High Performance, Direct conversion Receivers." You can find it here

12th September 2012, 07:10 AM	#8
franzm diyAudio Member Join Date: Dec 2010	NE542 is a direct replacement for LM387.

12th September 2012, 10:18 PM	#10
jscherer diyAudio Member Join Date: Apr 2008	The NE542 is 0.7uV and the LM387 is 1.0uv so both are about the same. The LME49710 is listed as 2.5nV/Hz. So the LME49710 is it the lower noise winner which comes as no surprise. Given that bit of information, the bigger question I have is how should I go about reconfiguring the two preamps in the above circuits to use the LME49710.