Audio amplifier (part 2)

Thnaks for the info John ! Olivier

Hi JF,

If I build it in real, how can I measure the current in the MOSFETS ? Should I put small resitors in the sources (or drains) ?

Olivier

--
No, just use the voltage dropped across the load to calculate the
current.

For 30mA into 8 ohms, say, you\'d have:

     E = IR = 0.03A * 8R = 0.240 volts

Then, before applying power make sure Vin is grounded and the pots
are cranked to zero ohms between the gates and the diodes. 
 
After that, apply power and crank one of the pots until there\'s 240mV
across the load.  Then crank the other pot until the voltage across
the load falls to zero, and you\'re done.

     
JF

I still have a question ... Gain is R3/R4. If I want to increase the gain let say to 10, is it better to increase R3/R4 or put an other amp-op as preamp in front ?

Olivier

--- R3/R4 sounds funny; on my LTspice schematic it's R3/R2.

Anyway, whatever the reference designations are, here's how it should be with the gain set to 10 by R2/R1.

+----------------------------+ | | +V>---------------------|---+----------+-------+ | | | | | | | | |1K D | R2[1000] | R4 [POT]-------------[100]--+--|-\\ |K | | | >--------+ +-----+ +--|+/ |A | | | | CR2[1N4148] | [LOAD] R3[91] | | S | | | R5 [POT]-------------------------+----------+-------+

JF

John Fields wrote: Ooops wrong schema ! Yes it is R2/R1 !

My question was more on stability. Is it better to but a 10x preamp in front of U1 and set R2/R1 = 1 or just R2/R1 = 10 ?

Olivier

--
>Ooops wrong schema !
>Yes it is R2/R1 !
>
>My question was more on stability.
>Is it better to but a 10x preamp in front of U1 and set R2/R1 = 1 or
>just R2/R1 = 10 ?