[sdiy] Overdriving 4007

[harrybissell]

1) use two packages...

2) switch to the 4007 which has two complementary pairs
plus inverter. With the two pairs, you can add what would
be called 'emitter resistors' in a comp symmetry audio amp...

series resistor from the output of the N, and a series resistor from
the P... take your output from the center tap.

Set the idle current you want with the two resistors.  With like
1M feedback they could be 500 ohms or so. Now the dissipation is
controllable.

Use the "inverter" section for stage three, which should draw the least
power.

This would require two packages for a two channel solution as well...

H^) harry

Seb Francis wrote:
> 
> Harry Bissell Jr wrote:
> 
> > One other problem might be that you are using two stages
> > in linear mode. These will get hotter than normal. Make sure it
> > does not run TOO hot. Its probably Ok.
> >
> > The resistors do not limit this power... it flows from N to P channel
> > device
> > which are both 'half on'. It will be worst with no signal input
> >
> Yeah I did notice it uses a lot of current .. about 28mA with no
> signal.  This could be a problem because I plan to use the other 3
> buffers for a 2nd channel of distortion.  When 28mA was measured the
> other 3 inputs were hooked to 0V, so I'd imagine it would take more like
> 56mA when using all 6 buffers.  This equates to 840mW at 15V (the
> absolute maximum is dissipation on the datasheet is 700mW).
> 
> Any way round this?  A heatsink perhaps?
> 
> Seb