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?
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?
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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?
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
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.
The noise of that receiver is given mainly by the audio preamp (the circuit around Q1-Q3), not by the LM387. BTW, LM387A has lower noise than LM387.
I was looking at that section too. The topology seemed strange. I don't see a lot of common-base amplifier circuits. Its nice because the input impedance is low but I would imagine the more common CE-amp could be designed with lower noise transistor for lower over all noise, but how do you make the input impedance match to 50 ohms?
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