input buffer question

[floatinginput]

Hi,

I am trying to interface to an oxygen sensor and am interested in a
circuit with the following characteristics.

low output impedance.
single rail
bias into the 0 - 12V range.
High input impedance (~1Mohms)

I have seen many single rail op amp applications, yet they all require
either zener diode (frequency problems - especially low frequency) and
resistor ladders which place the input impedance into the 50kohm range
i.e. two 100k in parallel.

Anyone got any ideas how to build a simple single rail input input
buffer that yields > 1Mohm input resistance and relatively good low
frequency performance?

Thanks in advance


Competent

 

[Winfield Hill]

floatinginput wrote...

I am trying to interface to an oxygen sensor and am interested in
a circuit with the following characteristics.

low output impedance.
single rail
bias into the 0 - 12V range.
High input impedance (~1Mohms)

Don't most (automotive) oxygen sensors produce a 0 to 900mV output,
with no external bias needed? Any single-supply opamp follower or
non-inverting amplifier should work fine.

I imagine you'll want a 10M resistor to ground, etc., so the opamp
input won't be "floating" during the open condition the oxygen
sensor exhibits when it's cold.


--
Thanks,
- Win