http://www.intio.or.jp/jf10zl/LM386.htm
7.How to get 74dB by LM386 lm386.gif
LM386 is very popular IC also in Japan. It is used in Radio receiver. The
power of it (500mW) is enough for the personal use. But sometimes, the gain
of it (40dB) is not enough. Especially the direct conversion receiver depend
on all of its gain on the audio amplifier. And therefore, we must stay
sometimes the pre-amplifier before LM386. I will show you the way to get
the 74dB only with LM386. Please watch the circuit ! Rf is the feedback
control resister. By chanbeing the Rf you can tune the gain of this circuit as
follows.
Rf (ohm) gain
feedback
dB
resister
3.3 74
10 70
33 54
105 44
820 34
--Emailer_-1249716426 Content-Type: text/plain; charset="iso-8859-1"
Content-transfer-encoding: quoted-printable
Dear Sunamura-san, I like to read your web-site very much, and I repeated
some of your constructions. I especially like your LM386 70 dB AF amplifier
which I called =B3the Sunamura amplifier=B2 in our national Ham Magazine.
Now, I have some news for you. The other day I found in our national ham
magazine a new type of a rock stable VFO. They did not mention the first
inventor, but I will try to find out who it was. It is a =8CColumbus= =B9 egg=B9 and it can substitute syntesizers. It uses a CERAMIC RESONATOR, and
the frequency can be spread for about 100 kHz. I attach the electric diagram. The chief part s are the Ceramic Resonator CR and the variable capacitor
C1. I used a standard CR for 3.579 kHz which is used as a clock in American digital devices. After a short warm-up, when you turn the capacitor C1 you
can change the frequency for about 150 kHz - from 3440 to 3620 kHz. To cover the CW segnment of the 80 mteres band a variable capacitor of 140 pf is
enough. And the frequency is rock stable. The capacitors C2 and C3 must have a capacity similar to the own capacity of the CR. In my case it was 600
pF. I also tried the ceramic filter for 10,7 MHz with three pins, but then I had to use 50 pF for C2 and C3, because that was the capacity of the filter. I
used only two pins: the middle one and a side one - The frequency was between 10,9 and 11 MHz and the stability was very good. I also tried a 5,5 MHz
1 z 2 2015-07-29 00:06
http://www.intio.or.jp/jf10zl/LM386.htm
filter, but it did not work well - it gave a frequency of 17 MHz with only 10 kHz of spread. I am sure that you will make use of this oscilator - with your
tehcnical ingenuity. When I get some new CRs, I will make some more experiments. Meanwhile, I remain with best wishes, Bozidar Pasaric, 9A2HL, City of
Rijeka, Croatia, Europe My E-mail: [e-mail]
7.LM386g0��D�"�ł0_�0ąe�l
LM386 o0��e,gg0�0h0f0�0U�$Rn0�0D0IC g0Y0�]0Ś0o0��0�0�0�S�O_jn0ż�\OI{k0�0O0OŹ0Ś0f0D0~0Y0�500mWn0śQ�Ro0�P�N(uk0o0ASRg0Y0�W0K0W0
0
W0p0W0p0�]0n0)R_ ( 40dB )o0ASRg0o0!qD04XTL0B0�0~0Y0�yrk0�vĄcn0- ��c- �S�O_j�Ą0ń0�0Ż0�0ł0ó0�0�0�0�0ó0 �g0o0�0�0�0Ł0�0n0XE^hVk0Y0y0f0
n0�0ń0ó0ł0�OX[W0~0Y0�]0W0f0]0Ś0ą0H0k0�b0o0�LM386 n0MRk0MRnXE^hVł0Bf0-�Q0j0O0f0o0D0Q0j0O0j0�0~0Y0�B0j0_0k0LM386g074dB _�0ąe�lł0
:yW0~0Y0.�0�0�0�0�0n0Rf o0��0Ł0�0�0�0�0�0Ż0- ł0ó0�0�0�0�0- �bbg0Y0�2�F�ł0�cH0�0�Nk0�0c0f0
0hQSOn0)R_L0 Nn0h�n0�ik0ż�Ą{g0M0~0Y00
back to index
2 z 2 2015-07-29 00:06