Maker Pro
Maker Pro

Generating a DC bias

S

Stretto

Jan 1, 1970
0
What is a good way to generate a DC bias? I'm using an op amp to buffer a
voltage divider but I'm worried it may have issues with it's output
impedance(Obvious the DC bias should require much current but I'd rather
have a too low output impedance than too high). I've also read that it may
not be that good because of stability reasons at "low frequencies".
 
S

Stretto

Jan 1, 1970
0
"Tim Wescott" wrote in message

What is a good way to generate a DC bias? I'm using an op amp to buffer
a voltage divider but I'm worried it may have issues with it's output
impedance(Obvious the DC bias should require much current but I'd rather
have a too low output impedance than too high). I've also read that it
may not be that good because of stability reasons at "low frequencies".

Huh?

How low of an output impedance do you need, and over what frequency
range? Even cheap old things like the LM353 should have an output
impedance below 1 milliohm at DC. It just goes up from their unless you
do something fancy, but isn't that good enough?

And what sort of low frequency stability problems are you anticipating,
at what frequencies?

----------------------

1mOhm? All the op amps I have looked at recently have anywhere from 5mA to
30mA output current when shorted. At 10V this would be and effective output
impedance of 300ohms to 2kohms.

What I'm worried about is the bias not being stable all the time. The op amp
will be driving all the biases needed and needs to act like a low impedance
source and sink.

I read somewhere that the op amp bias has low frequency issues in some app
note. It think it was about single supply's. They didn't give any more
information about it.
 
Top