I have a supply of LM3900 single supply quad op-amps and want to use one as a 3 stage audio band pass filter.
I can not seem to sort out the biasing of the +ve input.
Some application notes show it tied to the positive rail via a 1M to 10M resistor and other application notes 75 k ohms. Wide variation here!
Can someone please give me some guidance on this?
From what I can gather the usual way of biasing the +ve input to half rail does not apply to this device.
jerd
"JERD" schreef in bericht news:Ss3sm.40974$ snipped-for-privacy@news-server.bigpond.net.au...
You'll have to look at the datasheet. This amplifiers are not using a long tailed pair but some kind of current mirror for the inputs. The datasheet - at least the one from Motorola I use - describes extensively the whys and hows of biasing.
petrus bitbyter
Have you looked at the data sheet yet? ... plenty of description and examples there
Quoting: 'Operation of this amplifier can be best understood by noticing that input currents are differenced at the inverting-input terminal and this difference current then flows through the external feedback resistor to produce the output voltage'. etc. It's all there.
Chris
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