Beginner:Two circuits with the same battery. No way.

Thread Starter

paldep

Joined Mar 3, 2016
41
I have an audio amplifier that use 3volt to power on and a preamplifier mic that use 1.5 volt. The preamplifier mic inputs in the amplifier through jack 3.5. When i try to use the same battery source the two circuits power on but it seems that there's inverse current flowing.What can i do? I'am a beginner. :( How can i isolate the two power input from each other ? When i use two different batteries all is going very well. When i Connect the circuits in parallel nothing happens! Thanks
 

ScottWang

Joined Aug 23, 2012
6,926
If the 3.7V is means that the lithium then when it full charge will be up to 4.2V, and its lower voltage is 3.2V, you could adjust the R1 values to match the current you want.

Two circuits with the same battery_3.7Vbat_paldep_ScottWang.gif
 

Thread Starter

paldep

Joined Mar 3, 2016
41
i used the circuit posted by Scottwang but the audio from the preamplifier does not pass in the amplifier. If i use separate batteries for each circuits then it work very well. it's very strange
 

ScottWang

Joined Aug 23, 2012
6,926
i used the circuit posted by Scottwang but the audio from the preamplifier does not pass in the amplifier. If i use separate batteries for each circuits then it work very well. it's very strange
Could you check the ID number of transistors for two amplifiers and labeling them in two parts and their position in the circuit.

Labeling the bjts from left to right as :
Preamp : Q1 , Q2, ...
Audio Amp : Q1, Q2, ...

Maybe you can draw the output circuit of the preamp and the input circuit of the audio amplifier.
 

Thread Starter

paldep

Joined Mar 3, 2016
41
F3K2SVFFHWN77C8.LARGE.gif FK0VHVFFHWN77CB.LARGE.jpg spy ear.jpg i made a reserch and found the schematics of my preamplifier. . the amplifier is based on a ka2209 ic. ,four 103k 100 v, one224k 100sg, two 104 cap, a 0.47uf and a 220uf10v and a led for the on off. sorry but i'm a beginner.
 

ScottWang

Joined Aug 23, 2012
6,926
If you have the capacitors as 1~10uF/10V~16V then in series with the output - C of Q1(2N2904), put the positive(+) with C of Q1 and the negative to the input of audio amplifier.
 
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