BBD input question

Started by loss1234, September 09, 2009, 12:21:36 AM

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loss1234

i know that a chip like the mn3207 has a very small peak to peak limit
and that i should run it from 5-10 volts.

however. in most circuits i make i adhere to +/- convention for my opamps (i never use Vbias)

So my question is this...do i NEED to run my opamps at a lower +/- to be compatible with the 9 volt rail of the BBD or is it really just a matter of making sure whatever signal i give the BBD is not too loud/big in volume?

this is often a source of confusion for me because i never know WHICH biases are important in a circuit. i almost always skip any bias related to the opamps as it usually just cuts the headroom (i use DC to DC converters, etc so i can get true +/- 15 rails in my boxes)
however, i dont want to skip any important Biases.

thanks so much for any help

Thomeeque

#1
 Basically you need to keep maximum ratings and operating conditions declared for every part of the circuit.

So if the part is MN3207, you check MN3207 datasheet and here you should find information how it should be biased and if the voltages coming from preceding stages could be dangerous for it's input. Unfortunately this concrete datasheet is bit hard to read since it is mixed japanese and english, but anyway you can derive somehow from it, that VI should not exceed -0.3 to +10V interval (relative to the ground node) and that input should be biased somewhere between 33/(33+47) and (33+50)/(33+50+47) of VCC (0.41*VCC to 0.64*VCC) again relative to the ground node (interval is derived from the schemo at last page).

I'm bit short of time now to go to more details, if you need more, just ask and be patient ;)

Just one note yet: for your situation would probably fit biasing method used e.g. in Boss HF-2 (C10+R17+VR6+C11+IC3)..

Cheers, T.
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Thomeeque

Quote from: Thomeeque on September 09, 2009, 05:11:37 AMVI should not exceed -0.3 to +10V interval

Sorry, it's -0.3V ~ +11V
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