Dear Hans-Albrecht, LF group,
You could bypass the problem altogether by using a single-supply op amp,
e.g. TLC271 or almost any other CMOS op-amp (but these are usually limited
to 15V total supply voltage), or LM324 / LM358 etc.
For just a few milliamps, it is very practical to use a diode/capacitor
voltage inverter to get several volts -ve by rectifying a square wave output
from, e.g. a 555 timer running at a suitable frequency. This is a
voltage-doubler type rectifier capacitively coupled to the square wave
source. If it is mains-powered, you can do the same thing using the +ve
supply transformer winding.
Don't worry about regulating the negative supply; op-amps are very tolerant
of supply voltage variations. But do make sure you filter the negative
supply with an R-C filter.
Cheers, Jim Moritz
73 de M0BMU
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Hans-Albrecht Haffa
Sent: 26 May 2005 15:45
To: [email protected]
Subject: LF: off topics: Inverter 12V/-12V wanted from DK 8 ND
Dear Lowfers,
for a cw-shaping circuit with an op-amp (second order key-klick filter by
Jim Moritz) I need an inverter for the negative supply of the op-amp...
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