On-Line #38 26 мая 1996

Железо

Iron - The pre-amplifier to the ADC. Wiring diagram of the electret microphone.

                 IRON


(C) L.D.E. SOFT


   I want to suggest another shemku designed for use with my A 
/ D converter circuit, which was published earlier. Who 
successfully repeated my scheme ADC probably noticed that for 
the digitization of the signals must be submitted to the ADC 
input signal of high amplitude (0.8-10c), mainly from the power 
amplifier. As you know, from the amplifier output power signal 
fall of distortion (noise) arising in the path of signal 
amplification. To get rid of a power amplifier, I suggest to 
build a small amplifier voltage input signal, I use sovmesno 
with this scheme the ADC. Also, this amplifier allows the 
connection of electret malogaboritnogo microphone to record 
speech (on the similarity SOUND BLASTER). Structurally, the 
amplifier is going on board the ADC, because has little 
kompanentov to build (from 4 / 6 parts). To connect the 
amplifier circuits of the ADC to remove the resistor 4.7kOm 
with the input circuit. Now the scheme: 

            C1 0.068> + 12c.
 Exit

                   10k (to ADC 3B).

                                         R3

                                    4 200k
 DA1-K140UD6> - 12c.
 R1-level input. signal


   Specifications:
Power supply - Bipolar + / - 6 ... 15 Volt
input level - from 150 to 500 mV.
output level - up to 3 volts
potreblyaemyy current from the power source (max) - 10 mA


   In what a diagram of the establishment does not need, 
provided the use of radio serviceable. 


   And shemka connect electret microphone:

            C1-0.47
                               > Output power
        \ +
         mf R1-15 kOm> General
        / -
                               > +5 V (power)


   Electret microphone, miniature, used in telefontrubkah, etc. 
With a microphone is a small feature, the thing that is 
necessary to observe the polarity of the microphone, in 
Otherwise, the latter fails. Slightly everlasting how to 
determine the polarity of the microphone. Terminals of the 
microphone technologically connected with the housing (as is 
seen with the naked eye). 


   Well, now everything.
                        (C) L.D.E. SOFT 1996
                       (095) 400-04-36 DENIS